Contact dermatitis, a type of eczema, is a skin reaction that results when you come into contact with substances your body is sensitive to. According to the National Eczema Association, the word “dermatitis” is used to describe any rash, but contact dermatitis differs from atopic dermatitis in that it develops as a result of something touching the skin versus being genetic.

There are two types of contact dermatitis: allergic dermatitis, which is an allergic skin reaction, and irritant dermatitis, which develops after encountering an irritating substance over time, according to the American Academy of Dermatology (AAD). Either way, the result is dry, red, itchy, sometimes blistering skin that could be accompanied by a burning or stinging sensation.

Contact dermatitis is very common and affects almost everyone at some point in their lives, the AAD notes. Michele Green, MD, a New York City-based dermatologist and RealSelf.com contributor, says it’s the root cause of most allergic reactions.

People working in occupations that require them to get their hands wet often, such as nurses, bartenders, and beauticians, tend to experience contact dermatitis more often than others, according to the AAD. Furthermore, the AAD points out, having asthma or hay fever, or experiencing other types of eczema, also put the body at increased risk. The environment plays a role, too. Extremes, whether it’s excessively hot or cold or excessively humid or dry, make it more likely for contact dermatitis to develop.

How will you know if you’re experiencing it? You might notice an immediate reaction where the skin came into contact with the substance. It could swell or even blister. Or, it could show up days to weeks later as dry, itchy, cracking skin. While the reaction to irritant dermatitis stays close to where the exposure happened, allergic dermatitis can spread away from the site, according to the National Eczema Association.

The symptoms of eczema can change over time, lessening and worsening at different points. A dermatologist can help you get to the bottom of what’s causing the irritation. Here are eight potential culprits.

1. Swimming Pools

Dr. Green says chlorine can be a trigger for some, leading to itchy, red skin or hives. According to the American College of Allergy, Asthma, and Immunology, swimming pools in general can dry the skin, which can make any existing rash worse. Does that mean it’s never a good idea to dive in? No way, but pay attention to your post-dip routine. “It is important to rinse off after swimming and apply protective moisturizer, which will act as a barrier for the skin,” Green says.

2. Shampoo

Ever dissect the ingredients list on your shampoo bottle? It’s a worthwhile exercise if you’ve been battling skin issues. Isothiazolinones (which keep bacteria from growing within the bottle) and cocamidopropyl betaine (a thickening agent) are commonly found in shampoos and can have a negative impact on the skin, according to the National Eczema Foundation.

3. Laundry Detergent

Though rare, it’s possible for ingredients used in laundry detergent to cause rashes, says Charles E. Crutchfield III, MD, a Minneapolis-based clinical professor of dermatology at the University of Minnesota Medical School and the medical director of Crutchfield Dermatology. Other personal care and household products (such as dishwashing soap) can cause issues, too. Added fragrance, regardless of whether it's noted on the packaging, is often the irritant.

4. Wrinkle-Resistant Fabrics

You probably already know that formaldehyde is bad for you, but you may be surprised to learn that formaldehyde may be lurking in your clothes. According to the National Eczema Association, the preservative may be packed into clothing items marked “permanent press” or “wrinkle-resistant.”

5. Dust

Airborne irritants such as dust can trigger contact dermatitis, Green says. Of course, it can be tough to avoid dusty environments, but you can take a proactive approach to resisting them. Green suggests applying a moisturizer containing ceramides. “[Ceramides] will act as a barrier to protect the skin and avoid known allergens,” she says.

6. Latex Gloves

You won’t necessarily see a reaction immediately. It can take years of touching a certain substance or material for an allergy to develop, according to the American Academy of Dermatology. For instance, if you work in a hospital and wear latex gloves for most of the day, you may eventually notice your hands becoming itchy and inflamed. That’s the result of your body developing an allergy to the gloves.

7. Metal on Your Jeans and Keys

As far as allergies go, nickel allergies are widespread. But nickel is hard to avoid — it’s everywhere. A study published in the September–October 2017 issue of the Brazilian Annals of Dermatology, for instance, found nickel was present in 100 percent of the keys the researchers tested. Even the button and metal snaps on your jeans can cause a reaction. The Mayo Clinic recommends ironing a patch onto your jeans to keep your skin from coming into direct contact with the metal.

8. Your Manicure

Are perfectly manicured nails worth the risk of developing swollen, blistering skin? Acrylic nails (and gel nails, too) have been linked to contact dermatitis on the fingertips, according to a study published in July 2015 in Skin Appendage Disorders. It’ll usually start with itchiness in the nail bed, which may then become dry and thickened. In most cases, all it takes is a stint of going au naturel for the nails to rebound.

A Final Word on Identifying the Cause of Your Contact Dermatitis Rash

It’s important to remember that the rash of contact dermatitis does not necessarily mean you have an allergy. Often, avoiding the product will clear away the rash. If you’re not seeing relief and the rash continues to occur or worsens, check with your dermatologist, who can recommend skin allergy testing to find the exact trigger.

8 Surprising Triggers for Contact Dermatitis