How to tell if a rash is serious

How can you tell if a rash is serious? Look for these signs

The itchy red bumps came out of nowhere and it's unclear whether the mystery rash is something that needs a doctor or if it can be soothed away with over-the-counter salves. And with summer in full swing, it's open season for rashes.

Theres a lot more opportunity to get into stuff that would cause a rash if the weather is nice, Dr. Carolyn Jacob, a dermatologist in private practice in Chicago, previously told TODAY.com. Culprits include everything from the sun and hot temps to brushes with plants and insects.

While it might be hard to pinpoint what is causing skin redness or itching, but contact dermatitis can be a common allergic reaction to skin care products. As it turns out, plenty of rashes respond well to over-the-counter remedies.

But some are a sign of something more serious, experts say.

When to seek to medical help

One important rule of thumb is to seek help if the rash came with other symptoms.

The majority of rashes are not life threatening, said Dr. Daniela Kroshinsky, an associate professor of dermatology at Harvard Medical School and director of inpatient dermatology and pediatric dermatology at Massachusetts General Hospital.

But, if youre feeling generally unwell and having a rash, that would be a reason to seek medical attention. Your primary care physician or dermatologist should be able to help you triage whether its something that should be seen and whether it needs to be seen urgently.

A rash can be a warning sign of a serious medical problem, such as an autoimmune disease or a Lyme infection, explained Dr. Laura Ferris, an associate professor of dermatology at the University of Pittsburgh Medical Center. Or it could simply be the result of a harmless, though vexing, insect bite or a brush past some poison ivy.

How can you tell if a rash is serious?

Here are some signs that your rash needs to be looked at by a medical professional:

1. If you have a fever or pain accompanying the rash.

You should get it checked out, Kroshinsky said. It could be a sign that you have an infection or are experiencing an allergic reaction.

2. If you have a sudden spreading of bruise-like lesions.

It might be a symptom of vasculitis and you need to get that looked at because your clotting cells might not be working right, Kroshinsky explained.

3. If your rash continues unabated.

You might have an infection, Kroshinsky said. Some rashes start out completely benign, but then a secondary infection develops because the integrity of the skin, which is a barrier against potential pathogens, has been disrupted, she explained. Signs of an infection include warmth and pain, yellow or green cloudy discharge and a bad odor.

4. Any rash that is widespread.

It can be a sign a major allergic reaction. For example, if this happens within two weeks of starting a new medication, the concern would be a reaction to the medication, Ferris said.

5. Rashes that start to blister should send you straight to the doctors office, unless you have good reason to suspect youve come in contact with poison ivy, both experts noted.

6. Purple spots that appear on your hands and feet could be a sign of a bacterial infection of the heart, Kroshinsky said. You can look at the skin as a window to the inside of the body, she explained.

7. If you develop a circular-shaped rash and youre in an area where Lyme disease is endemic, you should get it checked out, Ferris said.

If youre not ready to see your doctor, Kroshinsky suggested taking a photo of your rash.

It can be helpful when you come in to see us since the rash could have changed by then, she explained. This will tell us what it looked like before you started treating it with bacitracin or hydrocortisone. It will help us get a sense of the evolution of the rash.

Certain remedies and treatments can make a rash worse

Also, Kroshinsky counseled, keep in mind that the preparations you use to treat your skin condition might make things worse.

One thing to keep in mind is that if youre using a preparation with topical antibiotics, a significant number of people are allergic to bacitracin and neomycin, she explained. If the area you are treating becomes itchy or blistery you might want to stop using them and see a doctor.

And if you feel unsure about the rash, dont hesitate to seek medical advice from a dermatologist, Ferris said.

Were trained to distinguish between concerning and non-concerning rashes and getting you on the appropriate treatment, she added.

Unsure if it's a rash? Use our photo guide to spot common (and not-so-common) skin conditions.

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Can a Skin Blanching Test Tell You if a Rash is Serious? Experts Explain

When you press down on your skin for a few seconds and move your finger away, does that area of skin look lighter before it returns to its normal color? This is called blanching.

Some social media accounts are sharing this test as a hack for parents to determine if a childs rash requires medical attention. But can this blanching test actually be used at home to determine whether a rash is serious or not? Here's what experts think.

What is a skin blanching test?

Blanching of the skin is when the skin loses color from blood being displaced away from where pressure is applied, Dr. Dawn Davis, professor of dermatology and pediatrics at the Mayo Clinic in Rochester, Minnesota, told TODAY. For example, if I push on my skin and it looks slightly pale when I release my finger ... thats because Ive temporarily pushed or stopped the blood flow to that area, Davis added.

In medicine, this is called a diascopy, said Davis, and it involves taking a glass slide and pushing it onto the lesion or skin that appears red to see if the discoloration disappears with pressure to determine what type of rash or lesion is present.

You can also do this at home with a clear drinking glass, which makes it easier to see the skin underneath where the pressure is applied, Dr. Adam Friedman, professor and chair of dermatology at George Washington School of Medicine and Health Sciences told TODAY. Just be careful when applying pressure because you dont want to break the glass on the skin, Ive seen that happen before, said Friedman.

Why do some rashes "blanch" and others don't?

The reason why an area of skin is red is because the blood vessels are dilated or widened, and theres more blood flow to that area, said Friedman. So a blanchable or blanching rash occurs when the redness (erythema) or discoloration disappears with pressure, but then returns because the blood is still inside the vessels so it's being moved around, he added.

If a rash is non-blanching, that means the discoloration does not fade or disappear when pressure is applied, the experts noted. This is because there is bleeding or blood leaking from damaged vessels under the skin (also called purpura), which can be caused by a variety of conditions, Friedman explained. If the blood is out of the vessels you wont get blanching (because) you cant really move it around, he added.

Its important to note that rashes or discoloration can look different on different skin tones. Blanching of darker skin, and even recognizing there is erythema, is harder, said Friedman, adding that what may appear reddish or purplish on lighter skin can appear as brown, black or even off-white on darker skin. Being able to appreciate that blanching could require more pressure, said Friedman.

What are blanching rashes?

Oftentimes people believe that if something blanches, that means that its not harmful, but thats not true, they can be harmful, said Davis.

Extreme blanching of the skin can occur due to a lack of circulation, said Davis, which can be caused by frostbite or Raynauds phenomenon. The blood vessels constrict due to either a disease or temperature changes, and that can leave the tips of the fingers or the toes white, said Davis.

Another common blanching rash is caused by broken or dilated blood vessels (also called telangiectasia), which are typically benign and harmless, said Davis. However, there are times when theres not consistency between something blanching or not and being benign versus harmful, she said, adding that sometimes telangiectasia can be a sign of a more serious internal disease.

In the early stages of vasculitis (inflammation of blood vessels), which can be very harmful, a lot of times the lesions will blanch because theres not enough inflammation or destruction yet for the blood to leak, Davis explained.

Allergic reactions and insect bites can also cause blanching rashes, Friedman explained. If someone develops urticaria or hives, which can be due to a response to a food or medication that is blanchable, said Friedman. Hives are typically not dangerous, he added, but when coupled with symptoms like wheezing or difficulty breathing, can constitute an emergency.

It all goes back to what the rash is coming along with, Friedman added.

There are plenty of blanchable rashes that, in conjunction with systemic features (like fever, joint pain, organ dysfunction, diarrhea, vomiting), could be an emergency, says Friedman. There are multiple life-threatening drug reactions that have a blanchable rash that you absolutely dont want to dismiss, said Friedman.

Are non-blanching rashes serious?

There are a variety of things that can cause a purpuric rash or bleeding under the skin, said Friedman, and some are more serious than others.

Bacterial meningitis can cause a non-blanching rash, said Friedman, and as well as other bacterial infections such as meningococcemia and gonococcemia. (These) are actually a systemic infection thats manifesting in the skin because of the dissemination of that bacteria through the blood, said Friedman.

Purpuric rashes or vasculitis can also be caused by viruses like hepatitis C, autoimmune diseases, and even certain fungal infections in immunocompromised patients, Friedman explained.

In any of these cases, you wouldnt see this (non-blanching rash) alone patients would have other symptoms, said Friedman, adding that these concerning scenarios are relatively rare.

Meningitis symptoms include a high fever, stiff neck, severe headache, confusion, and vomiting, according to The Mayo Clinic.

The texture of a non-blanching rash can also offer clues. If you have whats called palpable purpura, meaning a non-blanchable rash thats raised that you can feel, our mantra in dermatology is its vasculitis until proven otherwise, said Friedman.

Vasculitis means theres inflammation attacking the vessels to the point where the vessels are being damaged or even destroyed, said Friedman, adding that this can be caused by severe drug reactions and malignancy (cancers). If you suspect the non-blanching rash is vasculitis, Friedman suggests getting workups done by a doctor to identify the cause.

Some non-blanchable rashes are not dangerous at all, said Friedman, and one of the most common is called benign pigmented purpura. Others include solar purpura, which are broad purplish patches typically found on sun-exposed areas of elderly people, said Friedman, and bruising or broken blood vessels from other activities. These are bothersome, but benign, he added.

While not all non-blanchable rashes are an emergency, its never a bad thing to go get it figured out, said Friedman, adding that individuals should watch out for any other symptoms.

If a patient develops a non-blanching rash, they should seek health care advice more proactively, said Davis.

Can this test be used to determine if a rash is serious?

The short answer is no you cant necessarily determine whether a rash is benign or serious only based on whether it blanches or not, said Davis, adding that there are multiple differentiating factors.

Unfortunately, theres no hard and fast rule of thumb to distinguish whether a rash is harmful or not based on any one specific characteristic, she added.

While the blanching test can help determine which type of rash you have, it is not a diagnostic test.

You want to distinguish between blanching and non-blanching, but then theres a laundry list of other things you need to flush out with respect to ... is it just a rash or is it a rash associated with something else, said Friedman. Both experts recommend watching out for other signs and symptoms if you have a rash.

One of these is a fever. I think a fever and a rash should always prompt some investigation, and absolutely fever and a non-blanchable rash, thats even more concerning, said Friedman.

If the child or the adult feels truly lethargic, toxic, or acutely febrile that would require urgent or emergent care, said Davis.

Another important thing to look out for is how the rash is spreading. If the rash progresses without explanation .... that could potentially be more concerning and you should seek medical evaluation sooner rather than later, said Davis.

Anytime you develop a rash, whether that be an adult or a child, its helpful to be mindful of your overall health at that moment, said Davis. Because often the skin is the window to the bodys overall health, she added.

This article was originally published on TODAY.com

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