Allergic reactions are the result of inflammation or irritation of parts of the body. Sometimes people may have an allergic reaction to soap, which typically only affects the skin. These reactions typically affect people who wash their hands frequently, such as health care workers. Although soap allergies rarely cause any serious medical problems, an allergic reaction to soap can cause severe discomfort and can be prevented or treated in a variety of ways.
An allergic reaction to soap is known as contact dermatitis. This condition is marked by a red rash which is typically painful and may also be itchy or cause blisters. This type of allergic reaction generally appears within 24 to 48 hours after the soap has touched the skin and may last for two to four weeks.
A soap allergy is the result of one of the fragrances or other chemicals in the soap generating an immunological reaction. People with a soap allergy have an immune system that responds to a fragrance or some other chemical as if it is something infectious. This causes an immune reaction which results in the release of chemicals, which causes inflammation and itching. Allergic reactions may also be caused by sodium lauryl sulfate -- an ingredient in soap that strips your skin of its natural oils.
One of the dangers of allergies to soap is that scratching an itchy portion of the skin can actually cause additional inflammation and irritation, increasing the intensity of the itch. Repeated scratching can result in neurodermatitis which makes the affected parts of the skin thick and unusually leathery. Skin affected by neurodermatitis may become permanently darker, raw or red due to the scratching.
Soap allergies can generally be diagnosed by the appearance of the inflamed skin and by asking a person about any recent changes in soaps or detergents used. Confirmation of the diagnosis can be achieved using "patch" testing, in which patches containing chemicals suspected of causing the allergy are applied to the skin. The patches are removed 48 hours later to see if an allergic reaction has developed; an additional examination 48 hours after patch removal can be performed to look for any delayed reactions.
The simplest way to treat an allergic reaction to a soap is to discontinue using any newly introduced soaps or detergents and to revert to brands, which have not caused an allergic reaction. Antihistamines can be taken orally to relieve the symptoms. Ointments which contain cortisone can also relieve itching and inflammation. Calamine lotion, cold compresses and milk/oatmeal baths may also relieve the itching.