Skin Allergies

What is Atopic Dermatitis? (Eczema)

Atopic dermatitis, also known as eczema, is an intensely itchy chronic allergic skin rash that usually is red, swollen, bumpy, patchy, and scaly. In early stages, the skin may ooze or blister and in later stages, the skin is commonly dry and thick. It commonly affects the face, neck, front of elbows and back of knees, but can affect any part of the body as well.

Ten to 20 percent of children and 1 to 3 percent of adults are affected, with about 80 percent developing the disease before age 5. Most patients have a personal or family history of atopy, with about 80% developing asthma and/or allergic rhinitis (“hay fever”). The itching associated with the condition usually is worse in the early evening and at night. Scratching worsens the condition and can lead to infection.

What is contact dermatitis?

Contact dermatitis is a rash caused by the skin coming in contact with something they have a reaction to. There are two broad types of contact dermatitis: allergic and irritant contact dermatitis.

How is contact dermatitis diagnosed?

Your doctor can help you determine if you have contact dermatitis by going through a thorough history with you regarding exposures. A physical exam of the skin helps determine if the rash is new or old and if they have peculiar shapes or distributions (eg. a V-shaped rash on the top of the feet in patients allergic to rubber slippers, or a rash around the finger where a ring is used).

If it is unclear if you have an allergy causing the rash, specialists may want to do a patch test in order to help narrow down or confirm potential contact allergies.

Allergic contact dermatitis:

Allergic contact dermatitis occurs in persons who have become allergic to a substance from previous exposure causing the skin to develop bumps, swelling, blisters, itch or thickening on the area that was in contact with the substance. Common sources are nickel, fragrances, rubber, cosmetics, preservatives, cobalt, neomycin. It happens after several hours to days of exposure.

Irritant contact dermatitis

Irritant contact dermatitis is not an allergy but a reaction to irritation to a substance that results in physical, chemical or mechanical trauma. Common irritants include detergents, acids, solvents, abrasive materials . The skin can become swollen, red, wet and oozing or dry and thick.

What is Urticaria? (Hives)

Urticaria is another name for “Hives”. The condition affects about 20% of the population at some time in their lives. It is characterized by raised, red welts on the skin associated with itching that may be mild or severe. Scratching, alcoholic beverages, exercise, and hot showers may worsen the itching.

 

What causes Urticaria?

Hives may be categorized as acute, lasting less than 6 weeks, or chronic, lasting more than 6 weeks. Acute (new onset) hives is generally due to certain foods, medications, insect stings, and infections. Foods such as eggs, shellfish, and nuts are common causes. Medication such as Aspirin and Penicillin also are common causes of hives. Episodes of hives lasting longer than 6 weeks are called chronic. Even after detailed testing and investigation, about 80% of hives have no known cause. Sometimes the immune system is causing the release of chemicals such as histamine. Other causes are physical in nature including pressure from belts and constricting clothing such as sock bands, vibration, cold or heat, or even water (aquagenic). Cholinergic Urticaria is another form of hives, due to an increase in body temperature with sweating, exercise, hot showers, or anxiety.

There are many other less common causes of hives such that a complete evaluation by your doctor is recommended.

Where can I find references and further information for Urticaria (Hives)?

American Academy of Allergy, Asthma and Immunology
American Academy of Dermatology