Contact Dermatitis

Contact dermatitis is an inflammatory skin condition that occurs after exposure to an allergen or irritant. Specifically, allergic contact dermatitis is caused by a foreign substance coming into contact with the skin, which can lead to skin changes after reexposure to the substance. On the other hand, irritant contact dermatitis is caused by the non–immune-modulated skin irritation from repeated exposure to a substance.

Contact dermatitis is classified as a type IV (i.e., delayed) hypersensitivity reaction, also known as cell-mediated hypersensitivity. Type IV hypersensitivity reactions result from the interaction between a T-lymphocyte and the specific antigen to which they have previously been sensitized. 

Contact dermatitis is caused by exposure to an allergen or irritant, such as detergents, surfactants, extreme pH, and organic solvents. Other irritants include plants from the Anacardiaceae family (e.g., poison ivy, poison oak, poison sumac) and Compositae family (e.g., parthenium, ragweed, aster, sunflower, chrysanthemum, artichoke). Nickel metal, commonly found in belt buckles; fragrances in shampoos and hand soaps; hand sanitizers; latex; and dyes in textiles and cosmetic products, commonly cause contact dermatitis. Contact dermatitis can be acute, the cause of which is typically a strong irritant, or chronic, caused by recurring exposure to a weaker irritant. 

The signs and symptoms of contact dermatitis include an erythematous, dry, itchy, or burning rash that can develop within 72 hours after exposure to irritating substances. Vesicles, or tiny, thin-walled sacs filled with clear fluid, ranging in size from pinpoint to five millimeters, are commonly present at the site of exposure. Additionally, the skin can be dry, scaly, and fissured (i.e., cracked). Typically, rashes occur on the hands, arms, legs, and face. Irritation from chemical substances affects the body's most frequently exposed parts, such as the hands. 

Risk factors for contact dermatitis include age and occupation. Infants are at high risk for contact dermatitis due to prolonged exposure to wet diapers. Additionally, the elderly population are at increased risk due to impaired epidermal barrier function, delayed recovery after barrier damage, and decreased epidermal lipid synthesis of skin. Those assigned female at birth are more frequently affected, particularly those between the ages of 20 and 59. Occupational exposure to continuous moisture and repeated hand washing can cause dryness and irritation, increasing the likelihood of contact dermatitis. The occupations with increased risk are healthcare workers, housekeepers, cleaners, and food handlers. Additionally, those who work with chemicals, like beauticians, hairdressers, and construction workers, may be exposed to solvents that cause allergic contact dermatitis. 

Contact dermatitis is treated by removing or avoiding the triggering allergen. The individual may also be encouraged to stop scratching the area to avoid damaging the skin barrier and causing possible infection. Gloves can be worn to prevent nighttime itching. Over-the-counter calamine lotion and emollients (e.g., Aquaphor, Vaseline) can help reduce dryness and itchiness, and oral antihistamines (e.g., cetirizine) may be used if the pruritus is bothersome. Medications such as topical corticosteroids (e.g., hydrocortisone) can also be applied once or twice daily for two to four weeks or until symptoms resolve. Topical calcineurin inhibitors (e.g., tacrolimus/pimecrolimus) are commonly used in addition to corticosteroids.