Not all allergies are created equal. While irritant contact dermatitis requires a heavy exposure to an offending agent, a brief exposure to allergens can set off allergic contact dermatitis provided that sensitization has already occurred upon previous contact.

Mechanism of the allergic reaction

Unlike irritant contact dermatitis, allergic contact dermatitis is caused by an immune response over allergens. But both conditions may still coexist. The former is an inflammation of the skin occurring after direct contact with an allergen. The pathogenesis of the condition is divided into two phases: the induction and elicitation phase. During induction, the allergen causes sensitization to T cells that then differentiate and multiply in preparation for the next contact. During re-exposure or elicitation phase, these T cells are activated upon the presence of the antigen (allergen) and exert a full blown attack over the area where the antigen is found—the skin. This causes tissue damage resulting to eczema.

The symptoms do not appear until after a day or even several weeks and may occur on any parts of the body. Common clinical manifestations are:

• red, itchy rashes
• swelling
• presence of blisters which may crust and form scales
• thick and leathery skin

Poison ivy, poison oak, and poison sumac constitute the most common cause of allergic reactions in America. A person gets the rash from the sap or plant oil called uroshiol. Nickel and products coated with nickel is the most common cause of ACD in the world. Other sources are hair dyes, formaldehyde (in adhesives, disinfectants, shampoo, nail hardeners, mouthwashes, and preservatives), varnishes, chromate (used for tanning leather, and cement), cosmetics, perfumes, medicine (neomycin and benzocaine), latex, and a whole multitude of products.

What your Doctor can do for you

Patch testing will most likely determine the cause of the rashes if unrecalled by the patient. The patch is applied unto the skin (preferably the back) for 24-72 hours and the patient is advised not to take a bath or take corticosteroids for at least a couple of weeks prior to testing which may alter the results. The test results will be used to gain a conclusion of the disorder taking into account the person’s medical history and manifestations. Topical or oral corticosteroids are prescribed depending on the area affected and severity. Antihistamines are used for their sedating effect.

What you can do

As with all allergic reactions, the best way to treat allergy is to determine the cause and avoid the culprit. Cool compresses and oatmeal (colloidal) bath will help soothe the itchiness. Also, protect yourself from the allergen as much as possible. The growing market is producing a lot of products that may contain allergens—but they also provide alternatives too. For nickel jewelries, try coating the surfaces that touch the skin with transparent nail polish. And don’t depend too much on the hypoallergenic label. The term is very ambiguous. Try to do a research on other products that you might want to try.