Acneiform eruption refers to a group of dermatoses including 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...

, 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...

, folliculitis

Folliculitis

Folliculitis is the inflammation of one or more hair follicles. The condition may occur anywhere on the skin with the exception of the palms of the hands and soles of the feet.- Causes :...

, and perioral dermatitis

Perioral dermatitis

Perioral dermatitis, a condition related to acne vulgaris, consists of red papules that may appear microvesicular that typically affect the nasolabial folds , perioral area or perioccular area . It usually affects women between the ages of 20 and 45...

. Restated, acneiform eruptions are follicular eruptions characterized by papules and pustules resembling acne.
The term "acneiform", literally, refers to an appearance similar to acne

Acne

Acne is a general term used for acneiform eruptions. It is usually used as a synonym for acne vulgaris, but may also refer to:*Acne aestivalis*Acne conglobata*Acne cosmetica*Acne fulminans*Acne keloidalis nuchae*Acne mechanica...

.

The terminology used in this field can be complex, and occasionally contradictory. Some sources consider 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...

 part of the differential diagnosis

Differential diagnosis

A differential diagnosis is a systematic diagnostic method used to identify the presence of an entity where multiple alternatives are possible , and may also refer to any of the included candidate alternatives A differential diagnosis (sometimes abbreviated DDx, ddx, DD, D/Dx, or ΔΔ) is a...

 for an acneiform eruption. Other sources classified acne vulgaris under acneiform eruption. MeSH

Medical Subject Headings

Medical Subject Headings is a comprehensive controlled vocabulary for the purpose of indexing journal articles and books in the life sciences; it can also serve as a thesaurus that facilitates searching...

explicitly excludes perioral dermatitis from the category of "acneiform eruptions", though it does group acneiform eruptions and perioral dermatitis together under "facial dermatoses".