Allergic Contact Dermatitis
Allergic contact dermatitis is a delayed hypersensitivity reaction (the reaction to the allergen occurs 48–72 hours after exposure). The most common allergens causing allergic contact dermatitis often change with time, as certain chemicals come in or out of use in the manufacture of products that come in contact with the skin. Most recently, common causes of allergic contact dermatitis include nickel, chromates, rubber chemicals, and topical antibiotic ointments and creams. Frequent sensitizers in the general population also include fragrance, formaldehyde, lanolin (wool grease found in ointments and cosmetics), and a host of other common environmental chemicals.
- Nickel is found in jewelry, belt buckles, metal closures on clothing, and some cell phones.
- Chromates are used in the process of tanning leather for shoes and in cement, so they can affect construction workers who are in contact with cement.
- Rubber chemicals are found in gloves, balloons, elastic in garments, mouse pads, and swim goggles.
- Neomycin is common in triple antibiotic first aid ointments such as Neosporin® (and generic versions of Neosporin) as well as other combination preparations with other antibacterials (eg, Polysporin®). It may also be found in eye preparations and eardrops. Bacitracin is a common ingredient in antibiotic ointments and creams and can cause allergic contact dermatitis as well.
- Common allergen-containing products include cosmetics, soaps, dyes, and jewelry.
- Poison ivy is a frequent cause and is discussed separately.