Betamethasone for skin: creams, ointments, scalp foam and plasters

Betamethasone is a corticosteroid, a copy of a hormone the body makes naturally and distinct from the anabolic steroids associated with bodybuilding. Applied to the skin, it treats itching, swelling and irritation from eczema, contact dermatitis and psoriasis.

The NHS describes it as stronger than some other skin treatments such as hydrocortisone, and it is usually prescribed when other medicines have not worked. Brand names include Betnovate, Betacap, Audavate, Bettamousse, Betesil, Fucibet, Xemacort and Diprosone. Some products combine betamethasone with other ingredients for infections or additional skin conditions.

The medicine stops chemicals being released into the skin when you have an allergic reaction or when your skin is irritated. That reduces the swelling, redness and itching. The NHS says your skin should start to get better after a few days.

It is not effective for impetigo, rosacea or acne. Most betamethasone products count as potent, which means a stronger effect but also a higher chance of side effects than a mild steroid.

Most adults aged 18 and over can use betamethasone skin treatments. Children aged 1 or over can use most formulations, some creams and foams need the child to be 6 or over, and the medicated plasters are for adults only.

Tell the prescriber or pharmacist if you have had an allergic reaction to betamethasone or to another medicine, if you are breastfeeding, if you have impetigo, acne, rosacea (including perioral dermatitis) or plaque psoriasis, if you have an existing skin infection, or if you have broken skin, cuts or itch without redness.

For creams, ointments and lotions the NHS says to check with a doctor if there is no improvement after 2 to 4 weeks, with a maximum of 4 weeks before medical review; for children the check point is 5 days. In children, scalp products and foam are limited to 5 to 7 days. Medicated plasters are used for no more than 30 days. Long-term conditions such as eczema and psoriasis may need 1 to 2 weeks or longer.

Use a thin layer measured in fingertip units, with one unit covering an area twice the size of your palm. Leave about 30 minutes between this and other skin products, and about 10 minutes before a dressing; do not cover children's treated skin with bandages. Avoid naked flames and smoking because of flammability. If you miss a dose, use it when you remember unless the next is due. Swallowing it or a large overdose should prompt a call to NHS 111.

A burning or stinging feeling for a few minutes after applying it is the common one and settles within days, along with lighter or darker patches of skin. Serious problems affect fewer than 1 in 10,000 users and are more likely with prolonged use on large areas.

• Stop and seek help for skin swelling, yellow fluid or increasing redness, which can mean infection.

• Seek help for raised pus-filled bumps in psoriasis.

• Seek help for severe stomach upset, vomiting, fatigue, dizziness, fainting, muscle weakness or mood changes, which can mean the adrenal glands are affected.

• Seek help for confusion, increased thirst, frequent urination, rapid breathing or fruity-smelling breath, which can mean high blood sugar, and for any new vision problem.

• Call 999 for swollen lips, mouth or throat, severe breathing difficulty or a blistered rash that may be anaphylaxis.

After prolonged use the NHS advises reducing gradually over 2 to 4 weeks before stopping, to prevent a flare. Stopping abruptly can cause burning and redness over a larger area than the original patch. Long-term effects include thin skin with permanent stretch marks, adrenal, blood sugar and eyesight problems, and rare slowing of growth in children, which doctors monitor.

Do not use betamethasone on the face unless a doctor has told you to, and never near the eyes or eyelids. Suspected side effects can be reported through the Yellow Card scheme.

Betamethasone skin treatments are safe to use in pregnancy according to the NHS, since very little reaches the baby. They can be used while breastfeeding on the smallest areas for the shortest time; wash cream or ointment from the breasts and nipples before feeding, and keep the baby away from treated skin. There is no evidence of an effect on fertility.

It is very unlikely other medicines will affect it. Tell your prescriber if you take the HIV medicines ritonavir or cobicistat, the antifungal itraconazole, or any other steroid-containing product such as inhalers, tablets, injections, nasal sprays or eye and nose drops. Alcohol is allowed, and it does not affect contraception or vaccination.