When to Worry About a Rash in Adults

By Terez Malka, MD
Medically reviewed checkmarkMedically reviewed
January 21, 2022

Most rashes are not a sign of a dangerous condition, and it is safe to treat them at home.

If a rash persists, or is accompanied by other symptoms, it might be time to seek medical attention. 

In this article, I’ll identify 10 signs you should be concerned about your rash.

I’ll also discuss the different types of rashes, when to see a doctor or healthcare provider, and when K Health can help. 

What is a Rash?

Rash is a term that describes skin irritation, discoloration, or an abnormal change in texture.

Rashes can range from mild to severe, and can appear alone or along with other medical conditions.

Common causes of rashes include chronic skin conditions like eczema and psoriasis, allergic reactions, bug bites, and viral, bacterial, or fungal infections.

It is sometimes difficult to tell what has caused a rash by appearance alone.

Healthcare providers will consider many things, including the shape, size, area of the body affected, duration, symptoms, and history of your rash. 

Most rashes do not require any testing to diagnose, but some may require lab testing or referral to a dermatologist to diagnose.

Treatment will depend on the cause, but many rashes can be treated with over-the-counter creams and antihistamines.

More severe rashes may require prescription treatments.

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Types of Rashes

Rashes are generally categorized as infectious or non-infectious.

Examples of non-infectious rashes in adults include:

  • Contact dermatitis: This type of rash is caused by touching something that causes irritation or an allergic reaction that can cause skin to become itchy, red, blistered, dry, and cracked. Many people experience contact dermatitis when using a new laundry detergent or soap, or after contact with an irritant like nickel or poison ivy.
  • Eczema: Eczema can affect any part of the body, and is usually a long-term condition that can be managed with moisturizing creams and corticosteroid creams. While it tends to be more common in childhood, it affects about 16.5 million adults in the USA. Seven types of eczema exist, including atopic, discoid, varicose and pompholyx eczema. Atopic dermatitis is the most common form. It causes the skin to become itchy, dry, and cracked. 
  • Hives: Also known as urticaria, hives usually present as raised, red patches or welts on the body. They can be different shapes and sizes, can come and go, and can appear anywhere on the body. People with hives often complain of an itchy, stinging, or burning sensation. Hives are often caused by an allergic reaction, but can also be caused by exposure to cold, a viral or bacterial illness, or for unknown reasons. 

The following are some examples of infectious rashes:

  • Shingles: This rash consists of painful blisters and appears as a cluster down one side of the body. It’s usually preceded by a tingling feeling in the area affected, which can be anywhere on the body. Some people feel generally unwell or tired as well. 
  • Ringworm: Also called tinea corporis, this fungal infection causes round, scaly, mildly itchy lesions. 
  • Impetigo: This is a common bacterial skin infection caused by group A streptococcus or Staphylococcus aureus bacteria. It causes open, red, crusty lesions that may be either painful or itchy. Impetigo can occur alone, or with other symptoms like fever and feeling unwell. 

Signs You Should Worry About a Rash

Most rashes are not dangerous, and can safely be treated at home with antihistamines.

If your rash is accompanied by any of the following symptoms, however, you should speak with your doctor or primary care providers as it could indicate something more serious.

You have a fever

A high fever combined with a rash may indicate an infection such as herpes, measles, mononucleosis, scarlet fever, or many others.

Viral illnesses commonly cause rashes in children, and sometimes adults as well.

If you have a fever and symptoms of general illness with a rash, talk to your doctor or provider. 

If you have fever and a dark purple rash that does not lighten when you push on it, or severe headache or neck stiffness, this can be a sign of a brain or spinal cord infection.

Seek medical care right away.

The rash hurts

A painful or tender rash can be a sign of a bacterial infection like impetigo or cellulitis, or the viral infection shingles. 

The rash is widespread

If your rash involves large areas of the body, or quickly spreads to different areas, talk to your healthcare provider. 

The rash appeared suddenly 

Sudden onset of rash often represents an allergic reaction, though other types of rashes can also present quickly.

If your rash is accompanied by other symptoms of a severe allergic reaction such as difficulty breathing, mouth or throat swelling, or vomiting, you should be seen in person right away. 

The rash has lasted longer than a week

If your rash is getting worse or not improving with antihistamines and care at home, talk to your healthcare provider to find out if any testing is needed and figure out a treatment plan.

The rash is purplish in color

A dark, purplish rash, or a rash coupled with dark bruising, can sometimes be a sign of infection, blood clotting, or a blood vessel problem.

If you notice a dark purple rash that does not get lighter when you push on it, or a rash along with bruising or accompanied by bleeding or any kind, you should be evaluated right away. 

The rash is blistering

Blisters are small pockets of clear fluid under the skin.

Common causes of blisters include viral rashes, shingles, poison ivy or other allergic rash, or sunburn.

All of these can be safely managed at home.

But if blisters are large or severe, occur on the mouth or genitals, or are accompanied by fever or other symptoms, they can be a sign of more severe infection or allergic reaction.

If you have any of those signs, see a doctor or healthcare provider as soon as possible. 

You have difficulty breathing

Difficulty breathing is a serious medical emergency. If this happens to you and you have a rash, call 9-1-1 or go to an ER right away.

You may be experiencing a severe allergic reaction called anaphylaxis. 

The rash looks like a bullseye and you have had a tick exposure

If you have an oval-shaped or round rash that is red on the outside and more clear on the inside—like a bullseye—this can be a sign of Lyme disease if you have recently been bitten by a tick or live in an area where ticks are common.

This condition needs to be diagnosed by testing and treated with antibiotics, so you should talk with a doctor or provider.

You see signs of an infection

Infection can develop on any area of open skin, such as those caused by scratching an itchy rash.

Signs of infection include increased pain, new swelling, worsening redness, warmth to the touch, crusting, yellow or green discharge, and an unpleasant smell.

Many mild rashes can be managed at home with over-the-counter antihistamines, hydrocortisone cream, and cool compresses.

Avoid highly-fragranced bath products, detergents, and soaps when you have a rash. Instead use gentle, unscented products.

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When to See a Doctor or Healthcare Provider

Most rashes are not dangerous and will go away on their own.

Others can be an indication of more serious health conditions.

If your rash is accompanied by high fever, shortness of breath, or dark purple areas, you should be seen right away.

If your rash worsens or does not improve over 1-2 weeks, talk to your primary care provider.

How K Health Can Help

Did you know you can access online urgent care with K Health?

Check your symptoms, explore conditions and treatments, and if needed, text with a healthcare provider in minutes. 

K Health’s AI-powered app is based on 20 years of clinical data.

Frequently Asked Questions

How can you tell if a rash is serious?
Most rashes are not dangerous. A rash that is dark purple in color, involves the mouth or genitals, or is accompanied by high fever, difficulty breathing, or mouth or throat swelling needs to be evaluated right away. A rash that spreads rapidly or gets worse over time should also be evaluated by a healthcare provider.
Is a full body rash a symptom of COVID-19?
Some people do develop a rash with COVID-19. If you are concerned you may have been exposed to COVID-19 and have a rash, get tested for COVID-19 and isolate from others.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.

Terez Malka, MD

Dr. Terez Malka is a board-certified pediatrician and emergency medicine physician.

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