Is it red, bumpy, or blistered? Does it itch? Rashes come in many shapes and sizes and have many causes, but they all involve irritated, inflamed, or swollen skin.
Contact dermatitis is a frequently occurring rash caused, as its name suggests, by direct contact with an offending substance. In some cases, the reason is obvious because the rash develops quickly, but in other instances it takes some detective work to discover the culprit. Common causes of contact dermatitis include:
• nickel in earrings or other jewelry
• chemicals in rubber gloves, balloons, or garment elastic
• neomycin, a common ingredient in mainstream first-aid ointments
• lanolin (the oil from wool that is widely used as a moisturizer and lubricant)
• a number of ingredients in cosmetics, soaps, or dyes.
The skin can react to a substance after prolonged or repeated exposure or after just one exposure. The most dramatic irritant is probably poison ivy, to which most people react after being exposed to it on a single occasion.
At the 66th annual meeting of the American Academy of Dermatology in February 2008, dermatologist Susan T. Nedorost, MD, FAAD, presented research showing a positive link between frequent hand washing and irritant contact dermatitis, or hand dermatitis, among healthcare workers. While frequency of hand washing was the most important factor—those who washed their hands more than ten times per day were at greatest risk—Dr. Nedorost found that a patch test reaction to the widely used detergent sodium lauryl sulfate (SLS) significantly increased the risk of developing hand dermatitis.
Allergic contact dermatitis occurs in people of all ages from all ethnic backgrounds. Its symptoms can include scaly red or pink blisters or other areas of raised skin, which often have a geometric shape with straight edges, eyelid swelling, severe itching, and secondary bacterial infection. The skin may become thick and can develop painful ulcers, crusting, or scaling. Blisters that ooze are not contagious, and contact with the fluid in blisters will not cause the skin rash to spread to other parts of the body, nor will it affect other people.
Some rashes are so common that they are named for their cause. Poison ivy is in a class by itself, but you may also be familiar with hot tub rash, swimmer’s itch, and diaper rash. Hot tub rash is an itchy, tender, bumpy red rash that can create pus-filled blisters around hair follicles—especially on areas covered by swimsuits, which prolong the contact of skin with water contaminated by Pseudomonas aeruginosa bacteria. In most cases, the rash occurs within a few days of swimming in a poorly maintained hot tub or swimming pool. Improved sanitation and maintenance can help prevent the spread of this uncomfortable condition.
Swimmer’s itch, or Cercarial dermatitis, is produced by an allergic reaction to parasites from infected snails. The parasites are usually found in water birds or aquatic mammals, but they can also burrow into the skin of swimmers. Found throughout the world, these parasites are most likely to cause swimmer’s itch during summer months. Symptoms include tingling, burning, or itching of the skin, small blisters, and small reddish pimples that develop within a few minutes or days of swimming in contaminated water. The itching may last up to a week or more. Frequent exposure increases the rash’s intensity. Thorough towel drying, showering soon after swimming, and staying away from any shallow and marshy water next to the shoreline can help prevent this condition.
Another common summer affliction is heat rash, also called prickly heat or miliaria. Excessive perspiration damages surface skin cells and then traps sweat beneath the skin, producing tiny bumps that cause a prickly, stinging sensation. Active people in hot, humid climates, newborns in incubators, and bedridden patients with fevers are at greatest risk.
Diaper rash is an all-too common problem in infants. Its cause can be an allergic reaction to the soap used to wash cloth diapers, to some brands of disposable diapers or baby wipes, by prolonged exposure to wet or dirty diapers, or by tight-fitting diapers that rub against the skin.
Dermatologists and other experts recommend avoiding whatever is causing the reaction along with the common triggers of contact dermatitis, such as perfumes and other sources of fragrance, lanolin, nickel, latex, and the like. When the cause isn’t obvious, patch testing or skin biopsies may be needed to determine a diagnosis.
Some rashes have no known cause. For example, granuloma annulare is a chronic condition with a mildly itchy round rash that has reddish bumps on the back of forearms, hands, or feet. It tends to afflict children and young adults. Although sometimes associated with diabetes or thyroid disease, granuloma annulare remains a medical mystery.
So is lichen planus, which produces reddish purple, shiny, flat-topped bumps with an angular shape on wrists, ankles, lower legs, back, or neck. Some patients develop this condition in the mouth, genital region, hair, or nails, or thick patches of bumps may develop on the shins. Rare in the very young and elderly, lichen planus usually affects adults between 30 and 70. Some medicines cause the condition, and lichen planus may be linked to hepatitis C.
Pityriasis rosea is another common mystery rash. It produces large, scaly, pink patches of skin followed by additional patches that become itchy and inflamed on the back, chest, neck, abdomen, upper arms, or legs. Some evidence suggests that this condition is caused by a virus that does not seem to spread from person to person.
What You Can Do
When it comes to rashes, prevention is the best treatment. To prevent contact dermatitis, try to avoid irritating substances, wash any area that comes in contact with allergic substances, wear cotton gloves under rubber gloves for all wet work, protect the skin with frequently applied layers or skin-soothing natural salves, and avoid long, hot baths, which can dry the skin. Also use mild laundry soaps, and be sure clothes are well rinsed. Try not to rub or scratch a rash to guard against secondary skin infections.
To prevent diaper rash, keep your baby’s diaper area clean, cool, and dry with frequent changing. Air dry infant skin as much as possible, pat your baby dry with a towel instead of scrubbing skin, and avoid creams that contain boric acid, camphor, phenol, methyl salicylate, or benzoin tincture.
Conventional prescriptions for contact dermatitis and other rashes include oral antihistamines, topical steroids, ultraviolet light therapy and, in severe cases that cover large areas, oral steroids such as prednisone. Alternative treatments include oatmeal baths, which relieve itching and irritation. Most natural products stores sell colloidal oatmeal bath products, or you can make your own by finely grinding, boiling, and straining oatmeal water for topical application or for adding to bath water. Oatmeal’s phenols provide antioxidant and anti-inflammatory activity.
Salves and other preparations containing skin-soothing herbs like calendula, St. John’s wort, chamomile, and comfrey help speed healing, remove redness, reduce inflammation, and alleviate itching. Note that oil-based salves are not recommended for poison ivy, because they can spread the plant’s irritating compounds. Tea tree oil can be applied topically full-strength or as a wash to poison ivy and other rashes. Another all-purpose rash healer is green clay, which can be mixed with water or herb tea (like chamomile or calendula) and applied as needed.
When to Call a Doctor
Any rash that lasts more than a week, gets worse despite treatment, or is accompanied by other symptoms like fever needs professional evaluation. Chickenpox (small round blister like pimples that crust over) and measles (a raised red rash) are common among children but can also strike adults. Outcroppings of tiny, very painful blisters (often accompanied by flu like symptoms) in older adults may be shingles.
Increasingly common, Lyme disease often begins with a red, circular lesion that may be followed by a rash of small raised bumps on the torso and often by flu like symptoms. Even meningococcal disease and mononucleosis can begin with a rash.