A mustard plaster is a poultice

Poultice

A poultice, also called cataplasm, is a soft moist mass, often heated and medicated, that is spread on cloth over the skin to treat an aching, inflamed, or painful part of the body. It can be used on wounds such as cuts...

 of mustard seed

Mustard seed

Mustard seeds are the small round seeds of various mustard plants. The seeds are usually about 1 or 2 mm in diameter. Mustard seeds may be colored from yellowish white to black. They are important spices in many regional foods. The seeds can come from three different plants: black mustard , brown...

 powder spread inside a protective dressing and applied to the chest

Chest

The chest is a part of the anatomy of humans and various other animals. It is sometimes referred to as the thorax or the bosom.-Chest anatomy - Humans and other hominids:...

 or abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

 to stimulate healing. In times past and present, the mixture was spread onto a cloth and applied to the chest or back. The mustard paste itself should never make contact with the skin. Applied externally, black mustard is used in the treatment of bronchial pneumonia and pleurisy

Pleurisy

Pleurisy is an inflammation of the pleura, the lining of the pleural cavity surrounding the lungs. Among other things, infections are the most common cause of pleurisy....

.

Mustard oil

Mustard oil

The term mustard oil is used for three different oils that are made from mustard seeds:*A fatty vegetable oil resulting from pressing the seeds,...

 irritates mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s; therefore, excessive internal use has been known to cause stomach

Stomach

The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

 problems and kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 irritation. Breathing the vapors of a mustard plaster can trigger sneezing, coughing, asthma

Asthma

Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

 attacks, or eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 irritation. Leaving a mustard plaster on the bare skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 for too long will lead to burning, blisters, or potentially even ulcers. A mustard plaster should never be left on for longer than 30 minutes. The actual mustard paste never comes in direct contact with the skin, just the cloth on which it is spread.

A typical mustard plaster recipe includes powdered mustard (amounts vary from recipe to recipe) and flour combined with water or egg white. This is then spread on a layer of cotton or flannel cloth and placed on the body. Some old sources suggest that the mustard powder be blended with egg white rather than water to prevent blistering of the skin.

Mustard plasters should not be used on children under the age of 6. Black mustard should not be used in patients with ulcers, venous problems, or kidney disease.

Mustard plasters are common in Russia and other Post-Soviet states

Post-Soviet states

The post-Soviet states, also commonly known as the Former Soviet Union or former Soviet republics, are the 15 independent states that split off from the Union of Soviet Socialist Republics in its dissolution in December 1991...

 , and France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 (paper sinapism of Dr Jean-Paul Rigollot

Jean-Paul Rigollot

Dr Marcel-Jérôme Rigollot was a nineteenth century French doctor and antiquarian famous for his role in the identification of evidence of some of Europe's earliest inhabitants and his invention of the mustard plaster....

). It is a common belief there that mustard plasters stimulate the immune system, relieve pain and also have an anti-inflammatory effect. They are often used to treat common colds, runny noses, rheumatism

Rheumatism

Rheumatism or rheumatic disorder is a non-specific term for medical problems affecting the joints and connective tissue. The study of, and therapeutic interventions in, such disorders is called rheumatology.-Terminology:...

and problems with the respiratory system.