Patient information · Urgent care and allergy
Hives and allergic reactions
what is urgent, and what can wait
Hives are raised, intensely itchy weals that appear, move around and fade within a day. Most allergic reactions are limited to the skin and settle with an antihistamine. The distinction that matters is whether the reaction is affecting breathing or circulation — and that changes everything about what to do next.
Call 999 immediately if there is
- swelling of the tongue, lips, mouth or throat, or difficulty swallowing
- difficulty breathing, wheeze, noisy breathing or a persistent cough
- a hoarse voice or a feeling of the throat closing
- dizziness, faintness or collapse, or skin that is pale and clammy
- severe abdominal pain or vomiting alongside a rash
- a sense of impending doom — people often describe this before anything else
This is anaphylaxis. Use an adrenaline auto-injector into the outer thigh immediately if one has been prescribed, then call 999. Lie the person flat with legs raised, or sit them up if breathing is difficult. Never stand them up or let them walk, even if they seem to improve. A second dose may be given after five minutes if there is no response.
Using an adrenaline auto-injector
- Use it early. Adrenaline is safe and works best given at the first sign of a serious reaction — do not wait to see if things worsen.
- Into the outer thigh, through clothing if necessary. Hold it in place for the length of time stated on your device.
- Call 999 and say the word anaphylaxis.
- Lie flat, legs raised. Sit up only if breathing is hard; roll onto the side if vomiting or unconscious.
- Second dose after five minutes if there is no improvement. Always carry two devices.
- Go to hospital regardless, even if symptoms resolve completely — reactions can return hours later.
Hives (urticaria)
Hives are raised, pale or red weals on the skin, often surrounded by a flare, and usually very itchy. A characteristic feature is that individual weals come and go within 24 hours while new ones appear elsewhere — the rash appears to travel around the body.
In about half of cases no cause is ever identified. Common triggers include viral infections (particularly in children), certain foods, medicines including anti-inflammatories and some antibiotics, insect stings, heat, cold, pressure on the skin and exercise. Stress and alcohol tend to make existing hives worse rather than cause them.
Managing hives at home
Helps
- A non-drowsy antihistamine, taken regularly rather than only when the rash appears
- Cool showers, cool compresses and loose cotton clothing
- Keeping a diary of what preceded each episode
- Keeping the room cool, particularly at night
Makes it worse
- Heat — hot baths, saunas, hot rooms
- Alcohol, which dilates blood vessels and intensifies itching
- Anti-inflammatory painkillers such as ibuprofen in some people
- Scratching, which releases more histamine and spreads the weals
Higher doses of antihistamine
For persistent hives, specialists often use antihistamines at higher than the standard packet dose — sometimes up to four times — because the licensed dose is frequently not enough to control the itch. This should be done on medical advice rather than on your own initiative, but it is worth asking about if a standard dose is not working.
Swelling of the lips or eyelids
Deeper swelling of the lips, eyelids, hands or feet is called angioedema. It often accompanies hives and is uncomfortable rather than dangerous provided the tongue, mouth and throat are not involved and breathing is normal. If any of those are affected, treat it as an emergency.
Angioedema without hives, particularly recurrent episodes, can be caused by certain blood pressure medicines (ACE inhibitors such as ramipril or lisinopril) or, rarely, by an inherited condition. Both need proper assessment rather than antihistamines.
When to have it investigated
- hives lasting more than six weeks, or recurring over months
- any reaction that involved breathing, swelling of the throat or faintness — you need an allergy assessment and probably an auto-injector
- reactions to a specific food, medicine or sting that you need identified
- hives with joint pains, fever or weight loss, or weals that leave bruising and last more than a day
- reactions that are affecting sleep, work or school
Book an appointment if you need allergy testing, an adrenaline auto-injector prescription and training, an allergy action plan for a school or nursery, or investigation of long-standing hives. We offer allergy testing on site and can arrange specialist immunology input where it is needed.
Allergy testing and action plans
Same-day appointments most days, seven days a week, 9am–7pm, on Whitechapel Road.
Tower Bridge Hospital London
97–99 Whitechapel Road, London E1 1DT
WhatsApp 07903 284 189
info@mhwclinic.co.uk
Open Mon–Sat, 9am–7pm (closed Sundays until September)
In an emergency
Call 999, or go to the Royal London Hospital Emergency Department, Whitechapel Road, London E1 1FR.
When we are closed and it is not an emergency
Call NHS 111 or visit 111.nhs.uk.