Clive Anderson - AT THE DERMATOLOGIST INFLAMMATION OF the skin or eczema may be caused by contact with an offending substance. This contact dermatitis is actually two distinct diseases. One type of contact dermatitis is known as allergic contact dermatitis and is a true allergic condition. It is inflammation of the skin caused by exposure to a substance to which an allergic reaction develops. This type of contact dermatitis occurs in only 30 per cent of the cases.
Much more commonly occurring though is the other type of dermatitis. This is an irritant dermatitis, caused not by an allergic reaction but by contact with an irritating substance. Irritant contact dermatitis is a rash caused by excessive contact with irritants. These include water, soap, detergents, solvents, acids and alkalis. Irritant contact dermatitis may affect anyone providing they have had enough exposure to the irritant. Persons with atopic dermatitis are particularly sensitive. Most cases of hand dermatitis are due to an irritant.
CONTACT DERMATITIS
COMPLICATIONS
A contact dermatitis, allergic or irritant, can have a variety of manifestations. In mild cases there may be only redness and itching at the site of contact. In more severe cases blisters,
oozing, crusts and scabs may develop. To further complicate matters, the breaks in the
protective skin barrier may
lead to secondary bacterial infection.
If untreated an allergic contact dermatitis can spread to other areas of the skin. This spread is not because the condition is contagious it is instead the stimulation of the bodies immune system causes the irritation to occur in areas of the skin not directly exposed to the allergen.
There are over 3,000
substances in our everyday
environment that are capable
of provoking a contact allergic dermatitis and the list continues to grow. Common allergens include nickel, rubber, dyes, preservatives, fragrances and some plants.
ALLERGY TO NICKEL
One of the most common allergenic substances is nickel. Some 10 per cent of women are allergic to this substance. Nickel is found in a wide variety of substances from coins to doorknobs. Many chrome-plated objects contain enough nickel to produce an allergic reaction in a nickel-sensitive individual. It is in jewellery, and not only the less-expensive costume jewellery, even 14K gold contains a substantial quantity of nickel added to the gold to impart strength. This can be leached out by perspiration to trigger an allergy. Frequent offenders are clothing fasteners studs and buckles on jeans causing an itchy rash around the belly button. Stainless steel also contains nickel but it is so tightly bound that it is safe for most persons with a nickel allergy.
Fragrances and preservatives found in perfumes, cosmetics and toiletries are the next most common offenders. Avoiding fragrances can be tricky as even some products labelled as unscented may contain masking fragrances. The chemical additives in rubber products can cause an allergy. Ingredients in the rubber cause most cases of contact allergy on the feet. Adhesives in shoes are a frequent cause of contact allergic dermatitis and these may be found even in leather shoes.
SENSITIVE TO HAIR DYES
Some persons are sensitive to chemicals in hair dyes. Permanent hair dyes contain a potent allergen called paraphenylene-diamine (PPD). About one-quarter of persons who are allergic to PPD in permanent dyes will also react to substances found in semi-permanent dyes. Follow carefully the package instructions for patch testing before using any hair dye.
Neomycin is a common allergen found in both prescription and non-prescription topical antibiotic creams, ointments, eye drops and eardrops. It is also used in combination with other antibiotics and topical steroids in first-aid creams. People who are allergic to neomycin and treat their cuts abrasions and rashes with over-the-counter creams containing neomycin frequently develop neomycin-induced dermatitis.
Gold is another not
uncommon cause of an
allergic contact dermatitis.
Your Dermatologist can
diagnose most contact dermatitis from the location of the rash and a careful history. Sometimes the cause cannot be identified and a patch test has to be performed. Patch tests are safe and easy tests used to determine the contact allergen. Small amounts of the suspected allergens are applied to the skin on strips of tape. The tape is removed after two days when an allergy will show up as a red spot. Treatment consists mainly of avoidance of the allergen.
Dr. Clive Anderson is a Dermatologist and Venereologist.
