Rash
Encyclopedia
A rash is a change of the skin
which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch
, become warm, bumpy, chapped, dry, cracked or blister
ed, swell and may be painful. The causes, and therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members. The diagnosis may confirm any number of conditions.
The presence of a rash may aid associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythema
tous, morbilliform
, maculopapular
rash that begins a few days after the fever starts. It classically starts at the head and spreads downwards.
Uncommon causes:
Points to note in the examination include:
Human skin
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...
which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...
, become warm, bumpy, chapped, dry, cracked or blister
Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...
ed, swell and may be painful. The causes, and therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members. The diagnosis may confirm any number of conditions.
The presence of a rash may aid associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
tous, morbilliform
Morbilliform
The term morbilliform refers to a rash that looks like measles. The rash consists of macular lesions that are red and usually 2-10 mm in diameter but may be confluent in places...
, maculopapular
Maculopapular rash
A maculopapular rash is a type of rash characterized by a flat, red area on the skin that is covered with small confluent bumps. The term "maculopapular" is a compound: macules are small, flat discolored spots on the surface of the skin; and papules are small, raised bumps...
rash that begins a few days after the fever starts. It classically starts at the head and spreads downwards.
Differential diagnosis
Common causes of rashes include:- Food AllergyAllergyAn Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
- AnxietyAnxietyAnxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
. - Allergies, for example to food, dyes, medicines, insect stings, metals such as zinc or nickel; such rashes are often called hives.
- Skin contact with an irritantIrritationIrritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
- Fungal infection, such as ringworm
- Reaction to vaccinationVaccineA vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
- Skin diseases such as eczemaEczemaEczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
or acneAcne vulgarisAcne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring... - Exposure to sunSunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
(sunburnSunburnA sunburn is a burn to living tissue, such as skin, which is produced by overexposure to ultraviolet radiation, commonly from the sun's rays. Usual mild symptoms in humans and other animals include red or reddish skin that is hot to the touch, general fatigue, and mild dizziness. An excess of UV...
) or heatHeatIn physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between... - FrictionFrictionFriction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
due to chafing of the skin - IrritationIrritationIrritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
such as caused by abrasives impregnated in clothing rubbing the skin. The cloth itself may be abrasive enough for some people - MenstruationMenstruationMenstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...
- Secondary syphilis
Uncommon causes:
- Autoimmune disorders such as psoriasisPsoriasisPsoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
- Lead poisoningLead poisoningLead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
- PregnancyPregnancyPregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
- Repeated scratching on a particular spot
- Lyme DiseaseLyme diseaseLyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
Diagnostic approach
The causes of a rash are extremely broad, which may make the evaluation of a rash extremely difficult. An accurate evaluation by a provider may only be made in the context of a thorough history (What medication is the patient taking? What is the patient's occupation? Where has the patient been?) and complete physical examination.Points to note in the examination include:
- The appearance: e.g., purpuricPurpuraPurpura is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin...
(typical of vasculitisVasculitisVasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
and meningococcal disease), fine and like sandpaper (typical of scarlet feverScarlet feverScarlet fever is a disease caused by exotoxin released by Streptococcus pyogenes. Once a major cause of death, it is now effectively treated with antibiotics...
); circular lesions with a central depression are typical of molluscum contagiosumMolluscum contagiosumMolluscum contagiosum is a viral infection of the skin or occasionally of the mucous membranes. It is caused by a DNA poxvirus called the molluscum contagiosum virus . MCV has no animal reservoir, infecting only humans. There are four types of MCV, MCV-1 to -4; MCV-1 is the most prevalent and...
(and in the past, small pox); plaques with silver scales are typical of psoriasisPsoriasisPsoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
. - The distribution: e.g., the rash of scarlet fever becomes confluent and forms bright red lines in the skin creases of the neck, armpits and groins (Pastia's lines); the vesicles of chicken pox seem to follow the hollows of the body (they are more prominent along the depression of the spine on the back and in the hollows of both shoulder blades); very few rashes affect the palms of the hands and soles of the feet (secondary syphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
, rickettsiaRickettsiaRickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...
or spotted feverSpotted feverA spotted fever is a type of tick-borne disease which presents on the skin.Types include:* Mediterranean spotted fever* Rocky Mountain spotted fever* Queensland tick typhus...
s, guttate psoriasisGuttate psoriasisGuttate psoriasis is a type of psoriasis that presents as small lesions over the upper trunk and proximal extremities; it is found frequently in young adults...
, hand, foot and mouth diseaseHand, foot and mouth diseaseHand, foot and mouth disease is a human syndrome caused by intestinal viruses of the Picornaviridae family. The most common strains causing HFMD are Coxsackie A virus and Enterovirus 71 ....
, keratoderma blenorrhagica); - Symmetry: e.g., herpes zosterHerpes zosterHerpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...
usually only affects one side of the body and does not cross the midline.
Overview of symptoms
| Skin disease | Symptoms | Usual area of body |
|---|---|---|
| Acne Vulgaris Acne vulgaris Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring... |
Comedones, papules, pustules and nodules. | Face, chest and back. |
| Acne Rosacea Rosacea Rosacea is a chronic condition characterized by facial erythema . Pimples are sometimes included as part of the definition. Unless it affects the eyes, it is typically a harmless cosmetic condition... |
Flushed appearance or redness. | Cheeks, chin, forehead or nose. |
| Boil Boil A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle. It is always caused by infection by the bacterium Staphylococcus aureus, resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue... |
Painful red bump or a cluster of painful red bumps | Anywhere |
| Cellulitis Cellulitis Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters,... |
Red, tender and swollen areas of skin | Around a cut, scrape or skin breach |
| Insect bite Insect bite Insect bites and stings occur when an insect is agitated and seeks to defend itself through its natural defense mechanisms, or when an insect seeks to feed off the bitten person. Some insects inject formic acid, which can cause an immediate skin reaction often resulting in redness and swelling in... |
Red and/or itchy bumps on the skin | Anywhere and can be sprinked randomly |
| Allergic reaction | Irregular, raised or flat red sores that appeared after taking medicine/drugs or eating certain foods | Anywhere |
| Hives | Bumps formed suddenly | Anywhere but usually first noticed on face |
| Seborrheic dermatitis | Bumps and swelling | Near glands |
| Cradle Cap Cradle cap Cradle cap is a yellowish, patchy, greasy, scaly and crusty skin rash that occurs on the scalp of recently born babies. It is usually not itchy, and does not bother the baby. Cradle cap most commonly begins sometime in the first 3 months... |
Dry, scaly skin | Scalp of recently born babies |
| Irritant contact dermatitis Irritant contact dermatitis Irritant contact dermatitis is a form of contact dermatitis that can be divided into forms caused by chemical irritants and those caused by physical irritants.-Chemical irritant contact dermatitis:... |
Red, itchy, scaly or oily rash | Eyebrows, nose, edge of the scalp, point of contact with jewellery, perfume or clothing. |
| Allergic Contact Dermatitis caused by poison ivy Poison ivy Toxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it... , oak or sumac Sumac Sumac is any one of approximately 250 species of flowering plants in the genus Rhus and related genera, in the family Anacardiaceae. Sumacs grow in subtropical and temperate regions throughout the world, especially in Africa and North America.... |
Red, itchy, scaly or oily rash; can also be weeping or leathery. | Anywhere that came in contact with the irritant either directly or via transfer (e.g. from contaminated clothing.) |
| Allergic purpura | Small red dots on the skin, or larger, bruise-like spots that appeared after taking medicine | Anywhere |
| Pityriasis Rosea Pityriasis rosea Pityriasis rosea is a skin rash. It is non-dangerous but may inflict substantial discomfort on some people... |
Started with a single scaly, red and slightly itchy spot, and within a few days, did large numbers of smaller patches of the rash, some red and/or others tan | Chest and abdomen |
| Dermatitis herpetiformis Dermatitis herpetiformis Dermatitis herpetiformis , or Duhring's disease,Freedberg, et al. . Fitzpatrick's Dermatology in General Medicine. . McGraw-Hill. ISBN 0-07-138076-0. is a chronic blistering skin condition, characterised by blisters filled with a watery fluid... |
Intensely itchy rash with red bumps and blisters | Elbows, knees, back or buttocks |
| Erythema nodosum Erythema nodosum Erythema nodosum is an inflammation of the fat cells under the skin characterized by tender red nodules or lumps that are usually seen on both shins... |
Large red bumps that seem to bruise and are tender to touch | Anywhere |
| Psoriasis Psoriasis Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of... |
White, scaly rash over red, flaky, irritated skin | Elbows and knees |
| Erythema multiforme Erythema multiforme Erythema multiforme is a skin condition of unknown cause, possibly mediated by deposition of immune complex in the superficial microvasculature of the skin and oral mucous membrane that usually follows an infection or drug exposure... |
Red, blotchy rash, with "target like" hives or sores. | Anywhere |
| Measles Measles Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses... |
Red rash that is raised with a fever or sore throat. | Usually starts first on the forehead and face and spreads downward. |
| Chickenpox Chickenpox Chickenpox or chicken pox is a highly contagious illness caused by primary infection with varicella zoster virus . It usually starts with vesicular skin rash mainly on the body and head rather than at the periphery and becomes itchy, raw pockmarks, which mostly heal without scarring... |
Multiple blisters with a fever, cough, aches, tiredness and sore throat. | Usually starts first on the face, chest and back and spreads downward. |
| Shingles | Red blisters that are very painful and may crust | Anywhere |
| Fifth Disease Fifth disease Erythema infectiosum or fifth disease is one of several possible manifestations of infection by erythrovirus, previously called parvovirus B19. The disease is also referred to as slapped cheek syndrome, slapcheek, slap face or slapped face. In Japan the disease is called 'apple sickness' or... |
Started as a fever and then developed a bright red rash | Cheeks |
| Warts | Soft bumps forming that don't itch and have no other symptoms | Anywhere |
| Ringworm | Bald spot on the scalp or a ring of itchy red skin | Anywhere |
| Syphilis Syphilis Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis... |
Rash that is red but not itchy | Palms of hands or soles of feet |
| Jock itch Jock itch Tinea cruris, also known as crotch itch, crotch rot, Dhobie itch, eczema marginatum, gym itch, jock itch, and ringworm of the groin in American English is a dermatophyte fungal infection of the groin region in either sex, though more often seen in males... , yeast infection or diaper rash Diaper rash Irritant diaper dermatitis is a generic term applied to skin rashes in the diaper area that are caused by various skin disorders and/or irritants.Generic rash or irritant diaper dermatitis is characterized by joined patches of erythema and... |
Red itchy rash | Groin |
| Tinea versicolor Tinea versicolor Tinea versicolor is a condition characterized by a rash on the trunk and proximal extremities. Recent research has shown that the majority of Tinea versicolor is caused by the Malassezia globosa fungus, although Malassezia furfur is responsible for a small number of cases... |
Light coloured patches | Anywhere |
| Impetigo Impetigo Impetigo is a highly contagious bacterial skin infection most common among pre-school children. People who play close contact sports such as rugby, American football and wrestling are also susceptible, regardless of age. Impetigo is not as common in adults. The name derives from the Latin impetere... |
Crusted, tan-colored sores | Near nose or lip |
| Scabies Scabies Scabies , known colloquially as the seven-year itch, is a contagious skin infection that occurs among humans and other animals. It is caused by a tiny and usually not directly visible parasite, the mite Sarcoptes scabiei, which burrows under the host's skin, causing intense allergic itching... |
Bite-like sores that itch and spread intensely | Usually start on hands or feet and spread everywhere |
| Rocky Mountain spotted fever Rocky Mountain spotted fever Rocky Mountain spotted fever is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” , “São Paulo fever” or “febre... |
A fine rash with a fever and headache | Usually start on arms and legs including the hands and feet |
| Lupus erythematosus Lupus erythematosus Lupus erythematosus is a category for a collection of diseases with similar underlying problems with immunity . Symptoms of these diseases can affect many different body systems, including joints, skin, kidneys, blood cells, heart, and lungs... |
A butterfly rash with achy joints | Forehead and cheeks |
| Jaundice Jaundice Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid... or sign of hepatitis Hepatitis Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"... |
Yellowish | Skin, whites of eyes and mouth |
| Bruise Bruise A bruise, also called a contusion, is a type of relatively minor hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep into the surrounding interstitial tissues. Bruises can involve capillaries at the level of skin, subcutaneous tissue, muscle,... |
Blue or black area after being hit | Anywhere |
| Actinic keratoses | Scaly, pink, gray or tan patches or bumps | Face, scalp or on the backs or the hands |
| Keloid Keloid A keloid is a type of scar, which depending on its maturity, is composed mainly of either type III or type I collagen. It is a result of an overgrowth of granulation tissue at the site of a healed skin injury which is then slowly replaced by collagen type 1... or hypertrophic scar Hypertrophic scar Hypertrophic scars are a cutaneous condition characterized by deposits of excessive amounts of collagen which gives rise to a raised scar, but not to the degree observed with keloids. Like keloids, they form most often at the sites of pimples, body piercings, cuts and burns. They often contain... |
Scar that has grown larger than expected | Anywhere |
| Lipoma Lipoma A lipoma is a benign tumor composed of adipose tissue. It is the most common form of soft tissue tumor. Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults... |
Soft or rubbery growth | Anywhere |
| Milia Milia A Milium , also called a milk spot or an oil seed, is a keratin-filled cyst that can appear just under the epidermis or on the roof of the mouth. Milia are commonly associated with newborn babies but can appear on people of all ages... |
Lots of white spots | On the face of a baby |
| Molluscum or contagiosum | Small, firm, round bumps with pits in the center that may sit on tiny stalks | Anywhere |
| Sebaceous cyst Sebaceous cyst A sebaceous cyst is a term that loosely refers to either epidermoid cysts or pilar cysts . Because an epidermoid cyst originates in the epidermis and a pilar cyst originates from hair follicles, by definition, neither type of cyst is strictly a sebaceous cyst... |
Bump with a white dome under the skin | Scalp, nape of the neck or upper back |
| Skin tag | Soft, fleshy growth, lump or bump | Face, neck, armpits or groin |
| Xanthelasma Xanthelasma Xanthelasma is a sharply demarcated yellowish deposit of cholesterol underneath the skin, usually on or around the eyelids. Although not harmful or painful, these minor growths may be disfiguring and can be removed... |
Yellow area under the skin | Under eyelids |
| Melanoma Melanoma Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye... |
Dark bump that may have started within a mole or blemish, or, a spot or mole that has changed in color, size, shape or is painful or itchy | Anywhere |
| Basal cell carcinoma Basal cell carcinoma Basal-cell carcinoma is the most common type of skin cancer. It rarely metastasizes or kills. However, because it can cause significant destruction and disfigurement by invading surrounding tissues, it is still considered malignant. Statistically, approximately 3 out of 10 Caucasians may develop a... |
Fleshy, growing mass | Areas exposed to the sun |
| Squamous cell carcinoma Squamous cell carcinoma Squamous cell carcinoma , occasionally rendered as "squamous-cell carcinoma", is a histologically distinct form of cancer. It arises from the uncontrolled multiplication of malignant cells deriving from epithelium, or showing particular cytological or tissue architectural characteristics of... |
Unusual growth that is red, scaly or crusted | Face, lip or chin |
| Kaposi's sarcoma Kaposi's sarcoma Kaposi's sarcoma is a tumor caused by Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus . It was originally described by Moritz Kaposi , a Hungarian dermatologist practicing at the University of Vienna in 1872. It became more widely known as one of the AIDS defining... |
Dark or black raised spots on the skin that keep growing or have appeared recently | Anywhere |
| Erythema annulare centrifugum Erythema annulare centrifugum Erythema annulare centrifugum is a descriptive term for a skin lesion. The lesions form consists of redness in a ring form that spreads from the center . EAC was first described by Darier in 1916... (EAC) |
Pink-red ring or bullseye marks | Anywhere |