Contact dermatitis is inflammation of the skin that results in an itchy or painful rash, red bumps and sometimes even blisters.
The condition can be triggered when skin comes into contact with something that irritates it, such as a solvent or hair dye. Or it can result from an allergic reaction: Poison ivy is a famous cause of allergic contact dermatitis. 
Both irritant and allergic contact dermatitis share many of the same signs, symptoms and sources. (A particular metal might irritate your skin, for example, while your neighbor is actually allergic to it.) But finding out which type of contact dermatitis you have&mdash;and what exactly is causing it&mdash;can help your doctor determine the treatment you need. 
Irritant contact dermatitis
This is the more common of the two. 
Frequently related to work, irritant contact dermatitis may first appear on the hands. How quickly symptoms develop can depend on the irritant itself: A mild irritant (soap, for example) might not cause problems for a while, whereas a strong irritant (battery acid) might spark an immediate reaction. 
Common sources of irritation include adhesives, detergents and other cleansers, fiberglass, bacteria and solvents. 
Irritant contact dermatitis is more likely to be painful than itchy, according to the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=aaallergy" target="_blank">American Academy of Allergy, Asthma &amp; Immunology</a>. Additional signs and symptoms may include: 
<ul>
 <li>Dry, chapped skin.</li>
 <li>Patches of redness, swelling and scaling.</li>
 <li>A burning or stinging sensation.</li>
 <li>Sores and blisters that can erupt and crust over.</li>
</ul>
The longer you're exposed to the irritant and the more powerful it is, the more severe your reaction will be. 
Allergic contact dermatitis
An allergen is anything that triggers an immune response in your body&mdash;and there are thousands of potential allergens out there, according to the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=aad" target="_blank">American Academy of Dermatology</a>&nbsp;(AAD). 
Some of those most likely to cause an allergic skin reaction are: 
Antibiotic ointments. Ingredients in topical, over-the-counter ointments are frequent offenders, according to the&nbsp;AAD. 
Clothing and shoes. Among the hidden allergens in these items are dyes, fire retardants, leather and rubber. 
Metals. Nickel and other metals can trigger allergies in some people. You can find these metals in jewelry; dental fillings; and even in some foods, including soy products, cocoa powder and cashews. 
Fragrances. This includes perfumes as well as any scented product. 
Plants. Poison ivy, oak and sumac may be the most obvious. 
Allergic dermatitis usually develops soon after contact&mdash;often within a few hours, according to the AAD. Sweat or sunlight can act as a secondary trigger to the allergen; you might not react to a clothing dye until you perspire in it, for instance. 
Symptoms of allergic contact dermatitis are similar to those for irritant type, except that allergens also often cause itching. 
&nbsp;Who can get contact dermatitis?
The answer is anyone, according to the AAD. 
However, some things can make you more susceptible, such as having or having had: 
<ul>
 <li>Asthma.</li>
 <li>Atopic dermatitis (eczema).</li>
 <li>Hay fever.</li>
</ul>
Occupations that require repeated exposure to a substance also carry a high risk for contact dermatitis. Examples of people at higher risk because of their job include hairdressers, healthcare workers, janitors and mechanics. 
Diagnosing the problem
Relief from either type of contact dermatitis starts with a visit to your doctor. Tell him or her as much as you can about your symptoms, such as when they began and what you were doing or wearing beforehand. 
Your doctor might suggest patch testing if he or she suspects an allergic reaction. In that case, strips of tape containing small samples of various allergens will be applied to the skin on your back. Any reactions over the next several days might help pinpoint the source of your symptoms. 
Treatment
You may be able to get some relief early on by applying cold soaks and compresses to the affected area. To reduce itching and inflammation, your doctor might suggest an oral antihistamine or a topical corticosteroid. Other treatments, such as antibiotics or phototherapy, may be needed in severe cases. 
Preventing a reaction
To prevent future problems, you'll want to avoid contact with any offending substances. That can prove difficult, especially if the source is related to your job or the environment. However, you and your doctor can work on strategies for minimizing exposure. Wearing gloves and using barrier creams are two possible solutions. 
Also: 
If fragrances are a problem, look for products labeled fragrance-free. The term unscented means only that the scent has been masked, not that it has been removed. 
If your doctor identifies an allergen that's used in many products&mdash;propolis, for example, is found in most cosmetics&mdash;ask for help tracking down products that don't contain it. Your doctor may have access to, or be able to steer you toward, databases with that kind of information. 
Reviewed 3/31/2024

Understanding contact dermatitis 

This condition can be caused by allergies or an irritation of the skin.