A rash is the skin reacting, and its pattern tells why.
The outer layer of skin works like a brick wall: flat cells held together by natural oils, keeping water in and irritants out. When that wall is dried out, irritated, or invaded by a fungus or a mite, the skin turns red and itchy. Where the rash is, its shape, and what makes it worse usually point to the cause.
In plain words.
Common causes: dry skin (worse in winter, with age, and with soap and hot water), eczema, a reaction to something that touched the skin (a new soap, detergent, hair dye or artificial jewellery), prickly heat in summer, and fungal infection (ringworm, “daad”): a very itchy patch with a raised, red edge that slowly spreads, in the groin, at the waist, under the breasts or between the toes.
Scabies is a tiny mite that burrows into the skin. It itches intensely, worse at night, between the fingers, at the wrists, the waist and the private parts, and often several people in one home itch at once. Everyone in the home needs treatment on the same day, even those without itching.
Be careful with mixed creams sold over the counter that combine a steroid with antifungal and antibiotic medicines. On a fungal rash they calm it for a while, then it spreads wider and becomes hard to treat, and long use thins the skin. Itching with no rash is worth a blood test: it can come from liver, kidney or thyroid problems, diabetes, low iron, or a medicine.
Inside the skin’s barrier
Flat cells held together by natural oils make a tight wall. Water stays in, and soap, dust and germs stay out. The itch nerves below stay quiet.
When the wall dries or is damaged, gaps open. Water escapes, irritants get in, the skin turns red and the nerves send itch signals. Scratching breaks the wall further, and the itch grows.
A moisturiser, put on often, seals the gaps. Treating the cause, such as a fungus or scabies, lets the skin heal and the itch settle.
Go to hospital now if
- A rash with swelling of the lips, tongue or face, or with trouble breathing or swallowing: call 112. This can be a severe allergic reaction.
- Blisters or peeling skin, or sores in the mouth, eyes or private parts, especially after starting a new medicine: go to hospital now.
- A rash of small purple or dark red spots that do not fade when a glass is pressed on them, with fever or feeling very unwell: go to hospital now.
- Fever with a rash spreading over the body and feeling very unwell: go to hospital now.
Call 112 or go to the nearest emergency department. Ambulance: 108 (102 in some states).
See a doctor within a day or two if
- A rash began after starting a new medicine, even if it is mild
- A painful band of blisters on one side of the body or face (shingles): the same day if it is near the eye
- Itching keeps you awake at night, or others at home itch too
- The rash is oozing, crusted or painful
- Itching all over with no rash, or with yellow eyes
- The rash is not better after two weeks of simple care
Tests that help.
Not everyone needs every test. He decides which ones are worth doing for you.
| Test | What it tells |
|---|---|
| Often none | Many rashes are recognised by how they look. Clear photos help a great deal on a video call. |
| Skin scraping for fungus (KOH test) | A scraping from the edge of a patch, looked at under a microscope. |
| Blood count, blood sugar and thyroid (TSH) | For itching without a clear rash, or rashes that keep coming back. |
| Liver and kidney function | Both can cause itching all over. |
| Iron level (ferritin) | Low iron can cause itching. |
| Skin biopsy | Rarely: a small sample, taken by a skin specialist, for a rash that does not behave as expected. |
Have it ready.
Tick them off as you gather them. The ticks stay on this phone only.
Online, or in person?
Do not use creams that mix a steroid with antifungal and antibiotic medicines unless a doctor has prescribed one for a short time. On a fungal infection they make the rash spread and become stubborn, and long use thins the skin.
A video call can
- Recognise many rashes from good photos and your story
- Tell which rashes need a hospital and which can be cared for at home
- Prescribe the right cream or tablet, and stop the wrong ones
- Look for an internal cause of itching with blood tests
Needs a visit in person
- A skin scraping or biopsy, by a laboratory or a skin specialist
- Rashes that need to be felt, or looked at closely in good light
- Blood tests, at a laboratory or by home collection
- Any sign in the red box: that is an emergency
Talk it through with Dr. Arya.
Bring your reports and medicines to a video consultation. He goes through them with you, in plain words, and says clearly if you need to be seen in person.
Book a video consultationDr. Prabhat Arya · MBBS, MD (Internal Medicine) · Delhi Medical Council Reg. No. DMC-83759