Dermatitis is an inflammation of the skin, sometimes due to an allergy. Dermatitis is the same as eczema, and the terms can be used interchangeably. The following are types of dermatitis.

SEBORRHOEIC DERMATITIS

This condition is a red, scaly, itchy rash that develops on the face (particularly the nose and eyebrows), scalp, chest, and back. The cause of seborrhoeic dermatitis remains unknown, although many factors have been implicated. The widely present yeast, Malassezia furfur (formerly known as Pityrosporum ovale), is involved, as well as genetic, environmental, hormonal, and immune-system factors. The claim that seborrhoeic dermatitis is an inflammatory response to the yeast has not been proven. Those afflicted with seborrhoeic dermatitis have an unfavourable epidermic response to the infection, with the skin becoming inflamed and flaking. In children, excessive vitamin A intake can cause seborrhoeic dermatitis. Lack of biotin, pyridoxine (vitamin B6) and riboflavin (vitamin B2) may also be a cause.

In adolescents and adults, seborrhoeic dermatitis usually presents as scalp scaling (dandruff) or as mild to marked erythema of the nasolabial fold during times of stress or sleep deprivation. Corticosteroid drugs and drugs that kill microorganisms may help.

CONTACT DERMATITIS

Contact dermatitis results from a reaction to some substance that comes in contact with the skin. Common causes are detergents, nickel, certain plants and cosmetics. It may be treated with topical corticosteroids. A patch test may be performed in order to identify the cause.

Only the superficial regions of the skin are affected in contact dermatitis. Inflammation of the affected tissue is present in the epidermis (the outermost layer of skin) and the outer dermis (the layer beneath the epidermis). Unlike contact urticaria, in which a rash appears within minutes of exposure and fades away within minutes to hours, contact dermatitis takes days to fade away. Even then, contact dermatitis fades only if the skin no longer comes in contact with the allergen or irritant. Chronic contact dermatitis can develop when the removal of the offending agent no longer provides expected relief.

Common allergens implicated in contact dermatitis include the following:

• Nickel (nickel sulfate hexahydrate) – metal frequently encountered in jewelry and clasps or buttons on clothing.
• Gold (gold sodium thiosulfate) – precious metal often found in jewelry.
• Balsam of Peru (Myroxylon pereirae) – a fragrance used in perfumes and skin lotions, derived from tree resin (see also Tolu balsam).
• Thimerosal – a mercury compound used in local antiseptics and in vaccines.
• Neomycin – a topical antibiotic common in first aid creams and ointments, cosmetics, deodorant, soap and pet food. Found by itself, or in Polysporin or Triple Antibiotic.
• Fragrance mix – a group of the eight most common fragrance allergens found in foods, cosmetic products, insecticides, antiseptics, soaps, perfumes and dental products.
• Formaldehyde – a preservative with multiple uses, e.g., in paper products, paints, medications, household cleaners, cosmetic products and fabric finishes.
• Cobalt chloride – metal found in medical products; hair dye; antiperspirant; metal-plated objects such as snaps, buttons or tools; and in cobalt blue pigment.
• Bacitracin – a topical antibiotic found by itself, or as Polysporin or Triple Antibiotic.
• Quaternium-15 - preservative in cosmetic products (self-tanners, shampoo, nail polish, sunscreen) and in industrial products (polishes, paints and waxes).
• Colophony (Rosin) – Rosin, sap or sawdust typically from spruce or fir trees.
• Topical steroid - see steroid allergy.

Self-help at home

• Immediately after exposure to a known allergen or irritant, wash with soap and cool water to remove or inactivate most of the offending substance.
• Weak acid solutions [lemon juice, vinegar] can be used to counteract the effects of dermatitis contracted by exposure to basic irritants (phenol etc.).
• If blistering develops, cold moist compresses applied for 30 minutes 3 times a day can offer relief.
• Calamine lotion and cool colloidal oatmeal baths may relieve itching.
• Oral antihistamines such as diphenhydramine (Benadryl, Ben-Allergin) can also relieve itching.
• For mild cases that cover a relatively small area, hydrocortisone cream in nonprescription strength may be sufficient.
• Avoid scratching, as this can cause secondary infections.
• A barrier cream such as those containing zinc oxide (e.g. Desitin, etc.) may help to protect the skin and retain moisture.

PHOTODERMATITIS

This form of dermatitis occurs in people whose skin is abnormally sensitive to light. A cluster of spots or blister occurs on any part of the body exposed to the sun (photosensitivity).

Many medications and conditions can cause sun sensitivity, including:
•    psoralens, coal tars, photo-active dyes (eosin, acridine orange)
•    musk ambrette, methylcoumarin, lemon oil (may be present in fragrances)
•    PABA (found in sunscreens)
•    salicylanilide (found in industrial cleaners)
•    St John’s Wort, used to treat clinical depression
•    Hexachlorophene (found in some ℞ antibacterial soaps)
•    Contact with sap from Giant Hogweed. Common Rue (Ruta graveolins) is another phototoxic plant commonly found in gardens.
•    Tetracycline antibiotics
•    NSAIDs.
•    Fluoroquinolone antibiotic: Sparfloxacin in 2% of cases.
•    Amiodarone, used to treat atrial fibrillation
•    Pellagra

Photodermatitis can also be caused by plants. This is called phytophotodermatitis.

Prevention includes avoiding exposure to the sun:

• Stay inside during the brightest hours of the day, from noon to 3 p.m.
• Cover up: wear long sleeves, slacks, and a wide-brimmed hat whenever harsh exposure is probable. Remember that cloud cover does not provide protection from UV rays.
• Avoid chemicals that may trigger a reaction (do not, however, stop taking medication without consulting a doctor).
• Wear sunscreen at least factor 30 with a high UVA protection level.

The following foods or treatment may also help:

• Beta Carotene – found in carrots, not proven to be effective
• Omega-3 fatty acids – found in fish and flax seed
• Protein – will especially help individuals where malnutrition may be a contributing factor.
• Vitamin B3, Vitamin C, Vitamin D, and Vitamin E
• Green tea – antioxidants
• Calendula
• Aloe – external use

If pellagra is the cause, niacin is the specific treatment.

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