Contact Dermatitis

Rash on a human arm caused by contact with Poison Ivy (Toxicodendron (Rhus) radicans). This is a common source of contact dermatitis and allergic reaction caused by the substance toxicodendrol in the plant.
Poison ivy is a common source of contact dermatitis. Rashes, like the one pictured here, result from an allergic reaction to the plant. See more pictures of skin problems.
Bill Beatty/Visuals Unlimited/Getty Images

If you have an inflamed, itchy, red rash that burns, it could be contact dermatitis. Contact dermatitis (a type of eczema) is usually a rash caused when someone rubs against plants such as poison ivy or uses products with ingredients containing possible allergens, such as certain laundry detergents or soaps, cleaning chemicals or latex gloves.

There are two categories of contact dermatitis -- irritant and allergic. Irritant contact dermatitis happens when a chemical or other harsh substance damages the upper layer, or epidermis, of the skin, resulting in burns, blisters and skin ulcers. Almost any substance or environmental element can cause irritant contact dermatitis over a long enough period of time for people who have very sensitive skin -- even dry or warm air and humidity can cause it [source: Hogan]. Irritant contact dermatitis could be life threatening if the condition is untreated and leads to serious infection.


Unlike irritant dermatitis, allergic contact dermatitis happens when a person's skin comes in contact with something he or she is, well, allergic to. An allergen causes your immune system to have an exaggerated reaction when it comes in contact with a substance. Instead of finding a substance harmless, your immune system considers the substance dangerous and responds appropriately. Sometimes, it may take years and many exposures for a person to react to a certain allergen, such as soap or an ingredient in a moisturizer [source: Mayo Clinic].

Once the allergens enter the top layer of skin, they combine with natural skin proteins. White blood cells then transport the allergen-protein combination through the body. Because your immune system has a "memory," the next time you touch that particular allergen, your body will recognize it -- and react to it. Itching, pain and inflammation are all signs that your body is reacting to some allergen [source: CCOHS].

The good news is that contact dermatitis isn't fatal and should not be contagious. Although, with the itching and burning, it can certainly be rather unpleasant [source: Mayo Clinic]. Of course, there's always a chance that the allergen will cause other reactions, such as swelling of the mouth and airways, which can be life-threatening. If this happens, you should seek immediate medical attention.

Keep reading to learn more about irritant and allergic contact dermatitis.


Common Types of Contact Dermatitis

Not all dermatitis is a reaction to an allergen. Irritant contact dermatitis happens when you come in contact with a substance that damages the skin [sources: Dillon, Mayo Clinic]. The irritants remove oils and moisture from your epidermis. Without the natural protection normally provided by these, the irritants can penetrate more deeply and trigger the immune system, causing inflammation. The severity of irritant dermatitis depends on several factors, including how much irritant came in contact with the skin, the chemical makeup and strength of the irritant, how long and how often the skin is exposed, and whether or not the skin has a tendency to damage easily [source: CCOHS].

Like irritant contact dermatitis, allergic contact dermatitis is an external skin reaction (most allergic responses are internal reactions). However, allergic contact dermatitis is an overreaction in the body's immune system to an allergen, not an irritant. Say you're allergic to latex. The first time you come in contact with latex, you won't have an allergic reaction; your body uses that first contact to learn the allergen is harmful. The second time you touch latex, your body "remembers" that you're allergic and produces warning signs. The body's natural histamine, or a compound that is released by the body's immune system, rushes to the contact site and warns you -- with a rash and itchy skin [source: Dillon]. The body's response to the harmful substance, not the substance itself, produces the rash. Some people may have stronger allergic reactions than others due to hypersensitivity to certain substances [source: Dillon].


Everyone's immune system reacts differently to allergens. It's possible to start developing an allergic reaction to a substance that you have been exposed to for many years. Once the substance becomes an allergen to you, however, it will cause an allergic reaction for the rest of your life. Sometimes a substance may not be a problem until you are in the sunlight. A few products that can cause this type of "photocontact" dermatitis are sunscreens, creams and lotions containing sulfa medication and perfumes [source: Mayo Clinic].

The symptoms of contact dermatitis can be almost as varied as the substances that cause it. To see what some of these symptoms are, continue to the next page.


Contact Dermatitis Symptoms

Contact dermatitis can have many symptoms, though the symptoms will likely vary depending if you have irritant or allergen dermatitis.

Symptoms include:


  • Red rash or skin with a bumpy appearance
  • Red patches that may look like a burn
  • Itching
  • Blisters with fluid
  • Swelling
  • Topical pain and/or burning sensation [sources: Dillon, Mayo Clinic]

When you have irritant contact dermatitis, the symptoms immediately following the skin-irritant contact will range from a mild redness to severe pain and blistering. Your reaction will be localized to the contact site; the rash and blisters shouldn't spread. Some of these symptoms can be severe and may need medical treatment. For example, if blisters are draining fluid, you may need to apply an anti-infection medication and bandages [source: Mayo Clinic].

Some occupations that require people to come in constant contact with cleaning agents and chemicals can cause cumulative irritant contact dermatitis, which results in dry, painful and peeling skin. For example, health care workers and homemakers may wash their hands more than 35 times a day; they are more likely to have contact dermatitis than people who don't wash their hands as often. Hairdressers can experience similar symptoms because they are exposed to skin irritants such as hair dye [source: Hogan].

The symptoms of allergic contact dermatitis start the same as irritant dermatitis but have key differences. The first sign of an allergic reaction may be an itch when the allergen comes in contact with the skin. The itch can progress into redness, swelling or blisters that have a discharge. The reaction starts as a localized rash, but it may spread to a different place from the site of contact. Allergic contact dermatitis usually occurs about 12 to 48 hours from point of exposure and can last for several days, whereas irritant dermatitis reactions appear and fade more quickly [source: CCOHS, Berman].

If you develop symptoms of contact dermatitis, you're going to want to know how to treat it. Read on for treatment tips.


Treating Contact Dermatitis

To treat contact dermatitis, wash the area that comes in contact with an irritant or allergen as thoroughly and as quickly as possible. Try to pinpoint what caused the inflammation -- you'll want to avoid it in the future. If the source of the contact can be determined, the symptoms should disappear in one or two weeks [source: Mayo Clinic]. Sometimes it may be difficult to pinpoint the source because symptoms may not appear for up to two days after exposure [source: Berman].

Once you have contact dermatitis, you just have to treat the symptoms. To reduce inflammation and itchiness, apply a wet compress or washcloth soaked in water, milk or saline solution to the rash. Then apply a topical cream that has an anti-itch ingredient, which may also reduce inflammation. While calamine lotion will help stop the itching, it should not be used for extended periods of time [source: Schoenstadt]. Try to avoid scratching the area as much as possible, as persistent scratching can cause a skin infection and permanent scarring [source: Mayo Clinic]. Overuse of medications may cause other skin problems, so follow the recommended directions. In severe cases of contact dermatitis, a doctor may prescribe a corticosteroid cream or ointment. And if you develop a bacterial infection due to itching, you may have to take antibiotics [source: Berman].


The best way to treat contact dermatitis is to avoid getting it in the first place. To do this, you can get a patch test from your dermatologist, which will help you figure out if substances are irritants or allergens. During a patch test, the doctor will apply common allergens to your skin under adhesive tape; these allergens are left in place for up to 48 hours. If you develop a rash or bump on the skin that has been in contact with an allergen, you may be allergic to that substance -- and should avoid it [source: Mayo Clinic].

For more information on contact dermatitis, look over the links on the following page.


Lots More Information

 Related HowStuffWorks Articles

More Great Links


  • American Academy of Dermatology. "Poison Ivy, Oak & Sumac." (8/5/09)
  • Berman, Kevin, MD, PhD. "Medicine Definitions: Contact dermatitis." Mediline Plus. (8/4/09)
  • Canadian Centre for Occupational Health & Safety. "Dermatitis, Allergic Contact." (8/5/02)
  • Canadian Centre for Occupational Health & Safety. "Dermatitis, Irritant Contact." October 15, 2008. (8/7/2009)
  • Dillon, Brian T., MD. "Contact Dermatitis." WebMD (8/4/09)
  • Hogan, Daniel J., MD. "Contact Dermatitis, Irritant." eMedicine from WebMD: Webscape. (8/5/09)
  • Hubbard, Virginia, MD, and Rustin, Malcom, MD. "Patch testing for skin allergies." (8/5/09)
  • Mayo Clinic Staff. "Contact Dermatitis: Causes." Mayo Foundation for Medical Education and Research (MFMER). July 31, 2009. (8/5/09)
  • Mayo Clinic Staff. "Contact Dermatitis: Complications" Mayo Foundation for Medical Education and Research (MFMER). June 23, 2009. (8/5/09)
  • Mayo Clinic Staff. "Contact Dermatitis: Definition." Mayo Foundation for Medical Education and Research (MFMER). June 23, 2009. (8/5/09)
  • Mayo Clinic Staff. "Contact Dermatitis: Symptoms." Mayo Foundation for Medical Education and Research (MFMER). July 31, 2009. (8/5/09)
  • "Evening Primrose Oil." January 1, 2008. (8/5/09)
  • Schoenstadt, Arthur, MD. "Treatment for Contact Dermatitis." (8/5/09)
  • Stoppler, Melissa Conrad. "Eczema." February 11, 2008. (8/7/2009)