How to Identify a Skin Rash

Woman with skin rash on back and front of lower legs.
Skin Problems Image Gallery Bacteria, a fungal infection, an allergic reaction -- what could be the cause of this rash? See more pictures of skin problems.
Š Lisjak

Somehow, an itchy, red rash has appeared on your skin and you're racking your brain to figure out how it got there. As you ponder your pruritic predicament, the rash seems to be getting larger. Is your imagination getting the best of you, or could it be something serious?

In general, a rash is defined as a change in your skin's color or texture that is different from normal [source: WebMD]. When you spot a rash, you probably wonder where it came from. Although your skin does have natural defenses, things like viruses, fungi and parasites can breach those defenses and cause you to break out in a rash. Other common causes of rashes include reactions to certain medications and exposure to heat [source: Mayo Clinic].


A number of factors can influence where and how you get a rash. Your age can be a factor, as aging skin is particularly prone to certain skin rashes, such as shingles, while small children are prone to rashes from chicken pox and roseola [sources: National Institute on Aging, New Zealand Dermatological Society]. Similarly, your lifestyle can be a factor. For example, athletes tend to get hot and sweaty, which makes them more prone to conditions like heat rash [source: Mayo Clinic].

Some rashes will go away on their own -- poison ivy, for example, should go away within one to three weeks [source: Mayo Clinic]. Meanwhile, others can be serious and need the attention of a doctor. How do you know if a rash needs medical attention? If you can't identify the rash or its cause, if you have a fever, if the rash is painful or it just won't go away, then you should visit a physician.

If you've examined your rash and you want to gather some more intel before heading off to the doctor, read on to find out about the different types of rashes.


Types of Skin Rash

So, you've got a red, raised, super itchy rash and you want to figure out what it is. Unless you've been walking barefoot through poison ivy, it's going to take a little research, and probably a physician, to solve the puzzle. But you might be able to narrow down the possibilities by considering a few things. Basically, most rashes fall into one of the following categories:

  • Localized rashes caused by a bacterial or fungal infection
  • Localized rashes that are caused by direct contact with an irritant or an allergen
  • Localized or widespread rashes that are caused by an allergic reaction to some type of medication or a virus

To determine your rash type, consider what it looks like and what you've been exposed to such as any new medications, potential irritants or allergens. Then try comparing that information with descriptions of some common rashes, such as:


  • Heat rash: Small bumps that are either fluid-filled or look like blisters can be a result of heat rash, especially if you've been out in the heat, been sweating, and/or wearing tight clothing.
  • Intertrigo: If you have a bright red rash in moist areas where your skin rubs together (think under your arms, behind your knees, or in other skin folds), you may have intertrigo.
  • Medicine rash: If a rash suddenly appears after you've just started on a new antibiotic, anti-seizure medication or diuretic, you might have a medicine-related rash. This rash starts out as small red splotches that quickly spread to cover large portions of your skin.
  • Ringworm: Contrary to its name, there are no worms involved here. Instead, this rash is caused by a fungal infection. It looks like an expanding ring, which grows outward.
  • Swimmer's itch: If you've been swimming in not-so-clean water, you may have swimmer's itch, which is a mild rash of itchy red bumps caused by parasites [sources: Mayo Clinic, Cleveland Clinic]

While these are fairly common, there are some rashes that are even more so. Keep reading to see what they are and how they are likely to manifest on your skin.


Common Rashes

While rashes themselves are not unusual, some rashes are more common than others are, including the following:

  • Dermatitis: There are several types of dermatitis, an inflammation of the skin. Atopic dermatitis is a reoccurring condition, so you'll likely know already if you have this type of rash. Your skin will be itchy and inflamed, particularly in folds of skin like the elbows, knees and neck. Contact dermatitis can present as itchy red patches from an irritating source (irritant contact dermatitis) or bumps and blisters from an allergen (allergic contact dermatitis).Poison ivy and poison oak are examples of allergic contact dermatitis [source: Mayo Clinic]. With irritant dermatitis if the exposure is strong -- say to a harsh soap or chemical -- you can get a rash immediately [source: American Academy of Dermatology].
  • Shingles: If you've ever had the chicken pox, then you could get shingles. Once you get over chicken pox, the virus stays in your body and can become active later in life, resulting in shingles. This rash not only gives you blisters, but it also affects the nerves, causing you pain. You usually recover in three to five weeks, although you may still experience pain after the rash is gone [source: National Institute on Aging].
  • Pityriasis rosea: Also known as the Christmas tree rash, pityriasis rosea usually starts in one spot and then sweeps outward, sort of like the aforementioned tree. Unfortunately, scaly, itchy rashes are the only gifts associated with this Christmas tree [source: Mayo Clinic].

Even though they may feel like they're hanging on forever, particularly if they're itchy or uncomfortable, all of these rashes tend to be short-lived. But not all rashes are that accommodating, so read on to find out about rashes that hang around or recur.


Recurring Skin Rashes

It's bad enough to have to deal with a rash when it's a short-term condition like, say a reaction to poison ivy. But some rashes are even more irritating because either they never go away or, if they do, they keep coming back to annoy you.

Some common culprits in this category are:


  • Atopic dermatitis: Eczema is kind of a catchall term for inflammation of the skin, and there are many different types of it. The most severe and long lasting of these is atopic dermatitis. The causes of eczema -- including atopic dermatitis -- are unknown. Eczema is chronic, marked by periods of flare-ups. Although the itchy, red rash associated with atopic dermatitis can appear anywhere on the body, it is often found on the elbows, knees and face [source: National Eczema Association].
  • Granuloma annulare: Also known as lichen annularis, granuloma annulare is a chronic rash that forms in a ringed pattern of red or yellowish bumps that often appear on the feet, fingers and hands. In some cases, these ringed rashes are itchy [source: WebMD].
  • Lichen planus: Although it is sometimes associated with Hepatitis C, the cause of this skin disorder is generally unknown. Persons suffering from lichen planus will find shiny purple or reddish-purple flat-topped bumps on their skin. The rash can affect any area of skin, but it is most commonly found on the wrists, ankles, back, neck and lower legs [source: Cleveland Clinic].
  • Psoriasis: In general, psoriasis rashes have white or silver scales accompanied by patches of red, dry skin that can be itchy and/or painful. The degree to which this skin disease affects people varies -- some present with only a few rashes, while others have rashes all over their bodies. Like atopic dermatitis, psoriasis is marked by periods of flare-ups and there is no known cure. Persons with psoriasis can also develop psoriatic arthritis [source: Mayo Clinic].

Now that you've investigated some of the more common recurring skin rashes, read on to find out some of the causes of these and other rashes.


Skin Rash Causes

If the idea of getting an itchy, red rash doesn't sound appealing, it would seem that the best-case scenario would be to avoid getting a rash at all. However, that's not as easy as it sounds. Even if you have good personal hygiene, which certainly helps to keep your skin healthy, there are still ways that rash-causing agents can latch onto your skin.

Some known causes of rashes are:


  • Bacteria: A rash may be a sign that some bacteria have moved in, either right on your skin or somewhere in your body. Some diseases that are caused by bacteria cause rashes on your skin, like scarlet fever [source: Kids' Health]. Likewise, bacteria growing on the skin can also cause some skin infections, like intertrigo [source: American Academy of Family Physicians].
  • Fungus: Typically, fungi love moist, warm areas, so those hot, sweaty places on your skin look like prime real estate to a fungus. Fungal infections can be the guilty party if you're suffering from intertrigo (although bacteria can be a culprit, too) [source: Mayo Clinic]. One of the most common fungal skin infections is ringworm, which is also known as "jock itch" if you get it in the groin area and "athlete's foot" if you get it on your feet [source: Medline].
  • Virus: Chicken pox, measles and roseola are all examples of rashes caused by a virus [source: New Zealand Dermatological Society]. In adults, shingles is caused by the varicella-zoster virus, leftover from when you had chicken pox as a kid [source: National Institute on Aging].

With so many causes out there, it seems like everyone should be covered with rashes. Fortunately, that's not the case, but in the event that you do contract a rash, read on to find out some of the treatments available.


Skin Rash Treatment

With the number of possible causes, conditions and diseases out there, it seems almost inevitable that you'll one day find yourself with inflamed, unhappy skin. Whether you contract poison oak on a day hike, have a reaction to that new medication you're taking or you pick up ringworm while working at the local cat shelter, there's no need to worry that your skin woes will remain forever. There are many treatment options, even if your rash is chronic:

  • If you have a bacterial skin infection, you may be able to let it heal on its own, or you may need a doctor's attention. Some conditions, like intertrigo, can go away on their own if you practice good hygiene, keep the area dry and avoid tight clothing [source: Mayo Clinic]. But if you have a severe bacterial skin infection, you may need an antibiotic cream or other prescription medication [source: American Academy of Family Physicians].
  • Fungal infections are usually treated with antifungal medications. Over-the-counter antifungal creams are available, but if you have a particularly difficult or persistent fungus, you may need prescription oral antifungal medications [source: American Academy of Dermatology].
  • If you have a rash caused by a virus, the specific virus will determine the treatment. In general, when a virus is the cause, the symptoms of the rash are treated rather than the virus that causes it. For example, your doctor may suggest antihistamines or a topical anti-itch medication to help ease your itching [source: New Zealand Dermatological Society].

The bottom line is that although the skin does manage to protect itself quite well, there are hosts of potential invaders and irritants that can breach its defenses. If you have a rash, it's best to see your doctor so that he or she can identify the culprit, treat it and return your skin to good health.


For more information, follow the links on the next page.


Lots More Information

Related HowStuffworks Articles


  • American Academy of Dermatology. "Fungal Infections of the Skin." (Accessed 9/15/09)
  • American Academy of Dermatology. "Types of Eczema: Contact Dermatitis." (Accessed 9/15/09)
  • American Academy of Family Physicians. "Intertrigo." (Accessed 9/15/09)
  • Cleveland Clinic. "Common Rashes: Granuloma Annulare, Lichen Planus, and Pityriasis Rosea." (Accessed 9/15/09) hic_common_rashes_granuloma_annulare_lichen_planus_and_pityriasis_rosea.aspx
  • Cleveland Clinic. "Diaper Rash." (Accessed 9/15/09)
  • Cleveland Clinic. "Rashes/Red Skin." (Accessed 9/15/09)
  • Kids' Health. "About Skin, Hair and Nails." (Accessed 9/15/09)
  • Mayo Clinic. "Common Skin Rashes." Dec. 20, 2008. (Accessed 9/15/09)
  • Mayo Clinic. "Poison Ivy Rash: Treatments and Drugs." April 30, 2008. (Accessed 10/13/09)
  • Mayo Clinic. "Psoriasis." April 10, 2009. (Accessed 10/13/09)
  • Mayo Clinic. "Types of Dermatitis." April 25, 2008. (Accessed 9/15/09)
  • Medline Plus. "Tinea Corporis." (Accessed 9/15/09)
  • National Eczema Association. "All About Atopic Dermatitis." (Accessed 9/15/09)
  • National Institute on Aging. "Shingles." (Accessed 9/15/09)
  • New Zealand Dermatological Society. "Exanthems." (Accessed 9/15/09)
  • WebMD. "Skin Conditions: Common Rashes." (Accessed 9/15/09)