Your pharmacist is a good place to start

Inflammatory skin conditions such as eczema, psoriasis and contact dermatitis are among the most common reasons people come to a pharmacy counter. Most topical steroids are prescription-only, but mild ones — such as hydrocortisone 1% — can be bought over the counter for short-term use on flare-ups in adults and older children. A pharmacist cannot diagnose everything on sight, but they can show you how to use a cream properly, spot problems early, and tell you when self-care is no longer sensible.

It helps to bring the tube or the repeat prescription slip with you, along with a rough idea of how long you have been using it, how often, and which parts of the body you are treating. That detail turns a quick question into genuinely useful advice.

Getting the amount right: the fingertip unit

Mistakes with topical steroids usually come down to quantity — people often apply far too much, or too little for it to work. The fingertip unit (FTU) is a simple way to judge a dose.

• One FTU is a line of cream squeezed from the tip of an adult index finger to the first crease — roughly 0.5 g.
• It covers an area about the size of two flat adult palms.
• Typical adult doses: 1 FTU per hand, 2 for a whole arm or leg, 3 to 4 for the trunk, and 1 for the face and neck.

Apply it thinly, in the direction the hair grows, and rub in gently. It should sink in rather than sit on the surface as a shiny layer. Wash your hands afterwards unless your hands are the area being treated.

Which strength, and where to use it

Topical steroids are grouped by potency, from mild (hydrocortisone) through moderate and potent to very potent. The same tube can be perfectly suitable for one part of the body and too strong for another. Skin on the face, neck, armpits, groin and under the breasts is thinner and absorbs more, so it usually needs a milder product for a shorter time. Thick skin on the palms and soles may need something stronger to have any effect.

Worth asking your pharmacist:

• How often should I apply it, and is once daily enough?
• How long should I keep going — a short burst of five to seven days, or longer?
• Should I taper it down, or stop suddenly?
• Do I treat only the rash, or the surrounding skin too?

Side effects worth knowing about

Used correctly, topical steroids are safe and effective. Problems are more likely with potent products, large areas, long courses, or use under dressings and wraps.

• Thinning of the skin, easy bruising, visible tiny blood vessels and stretch marks
• Worsening acne or rosacea, and a spotty rash around the mouth
• Masking or worsening a fungal infection such as ringworm
• With very potent steroids over large areas, enough can be absorbed into the body to matter — particularly in children, where growth can be affected

Ask what is realistic in your case, and whether a weaker product, a break, or a different approach would suit you better. Do not stop a long course of a potent steroid abruptly without advice, as the skin can flare badly. If you have been using one for weeks or months, ask about a stepping-down plan.

Other creams, and things that can interact

Emollients and steroids are often used together, and the order matters. Ask which goes on first and how long to leave between them — commonly 15 to 30 minutes — and whether you should also use a soap substitute instead of ordinary soap.

Mention everything else you are putting on your skin or taking by mouth, including:

• Other prescription creams, gels and scalp preparations
• Antifungal or antibiotic creams, which may be needed if infection is present
• Medicines such as ritonavir or cobicistat, which can raise steroid levels in the body
• Dressings and bandages, including wet wraps, which increase how much is absorbed

One safety point that is easy to miss: paraffin-based emollients and some creams are flammable. Keep them away from naked flames, and do not smoke while wearing them or sit close to a fire.

When to see your GP

Go back to your GP or practice nurse if any of the following apply:

• The rash is not improving after about two weeks of correct use, or it is getting worse
• It looks infected — weeping, yellow crusting, pus, spreading redness, pain or fever
• You have a painful rash that is worsening quickly with clusters of blisters or small punched-out sores, and you feel unwell — seek urgent advice the same day
• The problem is widespread, or affects the face, eyelids, genitals or breasts and you have not been given specific advice
• It is a child and a mild steroid has not helped, or you are reaching for it often
• You are pregnant, breastfeeding, or using a potent steroid over large areas
• A mole has changed, or you have a sore that will not heal

Before you leave the pharmacy, it is worth running through a short list: What strength is this? Where exactly should I apply it, and for how long? How much is one dose? Which side effects should make me stop and seek help? Should I use emollients too, and which ones? When should I come back if nothing has changed? A few minutes of questions now can save weeks of guesswork.