The problem: red spots after the antibiotic
Your child’s middle ear infection or your own sinus infection is just getting better when, on day seven of treatment, red spots appear on the tummy and back, then on the arms and legs. It itches a little, and your child is playing as usual. The questions come straight away: an allergy? Keep taking it? Contagious?
With antibiotics, the most common form is a so-called maculopapular rash: red spots and small bumps, usually symmetrical, sometimes merging (DermNet: Drug eruptions). With penicillins and related antibiotics it usually appears 4 to 14 days after starting the medicine and, in the experience of the guideline authors, can still appear 5 to 10 days after the end of the course (Wurpts et al. 2020). There are also rare, severe reactions that need immediate treatment. The table helps you get your bearings. It does not replace a diagnosis; only a medical examination gives a clear answer.
| What you notice | When | What it may be |
|---|---|---|
| Red spots and bumps, symmetrical, often starting on the trunk, possibly itchy; otherwise you or your child are well, and the mouth and eyes are clear | With penicillins and related medicines usually 4 to 14 days after starting, sooner with repeat use (Wurpts et al. 2020) | Uncomplicated drug rash or a rash from the infection itself (Wurpts et al. 2020) |
| Raised, very itchy wheals that move around | With an immediate-type allergy usually within an hour of taking it (Wurpts et al. 2020), with first use also later (DermNet: Drug eruptions) | Hives, possibly allergic |
| Swelling of the lips, tongue, face or throat, difficulty breathing, dizziness, circulation problems | Usually soon after taking it | Severe allergic reaction (anaphylaxis) (Ring et al. 2021): 112 |
| Fever and feeling ill, then a red to purple rash with blisters, skin coming away, severe pain, sore patches in the mouth, eyes or genital area | Typically 1 to 3 weeks after starting (MSD Manual: SJS/TEN) | Stevens-Johnson syndrome or toxic epidermal necrolysis: 112 |
| High fever, widespread rash, swollen face, swollen lymph nodes | Usually 2 to 8 weeks after starting, sooner with penicillins and related medicines (DermNet: DRESS) | Severe hypersensitivity reaction (DRESS): see a doctor immediately, A&E |
Why it happens – and why cold and flu season plays a part
A delayed reaction of the immune system. The blotchy rash does not develop in minutes but over days: immune cells react to the drug with a delay. The guideline describes uncomplicated rashes of this type in children as follows: no involvement of the mucous membranes, no blisters, no skin detachment, general condition barely affected, complete fading within a few days (Wurpts et al. 2020). After stopping the medicine, such a rash usually subsides within a week (DermNet: Drug eruptions).
Often it is the infection, not the antibiotic. Many viral infections cause rashes themselves, and according to the guideline such rashes in children are often mistaken for a drug reaction (Wurpts et al. 2020). In a Geneva study, 88 children with a rash while on a penicillin or related antibiotic were later given the medicine again under medical supervision: the rash returned in only 6.8 %, and most had signs of a viral infection (Caubet et al. 2011). In adults too, a suspected allergy to these antibiotics is rarely confirmed, in studies in 7 % or fewer (Wurpts et al. 2020). In autumn and winter, colds, fever and antibiotics often come together, and with them the question of what triggered the rash.
A special case: glandular fever. When people with this viral infection are given amoxicillin or ampicillin, a rash often develops. Figures of 80 to 100 % used to be quoted; in a more recent analysis in children, it was 29.5 % with amoxicillin, and children without an antibiotic had a rash hardly less often, at 23.1 % (Chovel-Sella et al. 2013).
Rare, severe reactions. In Stevens-Johnson syndrome and toxic epidermal necrolysis, flu-like symptoms are followed by blisters, the skin comes away, and the mucous membranes of the mouth, eyes and genitals become sore. Both must be treated in hospital; the triggering medicines include antibiotics such as sulfonamides (MSD Manual: SJS/TEN). In DRESS, high fever, rash, often a swollen face and enlarged lymph nodes come together, and internal organs can be affected (DermNet: DRESS). That is rare, but it is the reason why every new rash on a medicine should be assessed by a doctor.
The solution step by step
| Step | What you do | Why |
|---|---|---|
| Straight away | Watch for emergency signs: swelling of the face or mouth, difficulty breathing, dizziness, blisters, peeling skin, sore mucous membranes, high fever. Then call 112 and hand over the pack | Medicines are among the most common triggers of anaphylaxis in adults (Ring et al. 2021); the British NHS names these signs as a reason for an emergency call (NHS: Antibiotics side effects) |
| The same day | Without emergency signs: do not leave out the antibiotic or change the dose on your own, but call the practice; outside surgery hours 116117. Say which medicine, since when, and when the rash began | Whether to continue, switch or stop can only be weighed up by the practice; stopping treatment early can harm the fight against the infection. For side effects, the NHS advises contacting the practice (NHS: Antibiotics side effects) |
| The same day | Photograph the rash in daylight, again the next day; note when it began and how it develops | The timing and appearance of the reaction count for later assessment (Wurpts et al. 2020) |
| Every day | Short, lukewarm showers, pat dry, loose cotton clothing, do not scratch, keep nails short; no new creams, oils or home remedies | New products can irritate further and make the course unclear |
| If it itches | Cool, damp compresses; medicines such as antihistamines or cortisone creams only on the advice of a practice or pharmacy | Mild allergic rashes are usually treated with antihistamines (NHS: Antibiotics side effects); which one is suitable is a matter for professionals |
| Afterwards | Have the suspicion entered in an allergy passport and, once the rash has gone, have an allergy specialist test whether there really is an allergy | The guideline recommends an allergy passport and testing because many suspected cases are not confirmed (Wurpts et al. 2020) |
What helps – and what doesn’t
| Measure or assumption | Assessment |
|---|---|
| Stopping the antibiotic yourself at the first spot | no: call the practice first; only it can weigh this up. With emergency signs, 112 |
| Simply carrying on and telling nobody | no: every new rash on a medicine belongs with the practice the same day |
| Itch gel from the medicine cabinet | only on the advice of the pharmacy; it does not answer whether the antibiotic is the trigger |
| Home remedies such as vinegar, quark or essential oils | not studied; on irritated skin they are more likely to irritate further |
| Cool, damp compresses | can feel pleasant; they do not replace a medical assessment |
| “One rash means a lifelong penicillin allergy” | not necessarily: only a small proportion of suspected cases are confirmed (Wurpts et al. 2020), (Caubet et al. 2011); so have it tested rather than just noted |
| “The rash is contagious” | a drug rash is not; if a viral infection is behind it, that may be |
Common mistakes
The mistake with the biggest consequences is to stop the antibiotic without consulting anyone, leave the infection untreated and “use up” the rest of the pack weeks later. Second: blaming the rash on the new shower gel and trying out new creams. Third: mistaking emergency signs such as sore lips, red eyes or blisters for after-effects of a cold. Fourth: taking no photos, so that later nobody knows what the rash looked like. Fifth: carrying a suspected penicillin allergy around for years without having it tested. And finally: overlooking a sore bottom in babies during antibiotic treatment. Diarrhoea is one of the common side effects (NHS: Antibiotics side effects); what helps then is explained in Nappy rash in babies: what helps and when it is thrush.
When to seek medical advice?
Call 112 straight away if
- your lips, tongue, face or throat swell, you struggle to breathe or speak, you feel dizzy or are about to lose consciousness (Ring et al. 2021), (NHS: Antibiotics side effects),
- blisters form, the skin comes away or hurts badly, or the mouth, eyes or genital area become sore (MSD Manual: SJS/TEN), (DermNet: Drug eruptions).
Go to a practice or A&E immediately with a rash and high fever, a swollen face or swollen lymph nodes, even weeks after starting the medicine (DermNet: DRESS).
Call the same day your GP or paediatrician, or 116117, with any new rash during an antibiotic course or up to about ten days after it, even if you otherwise feel well. With infants, with a fever that does not come down, or if your child is listless and drinking poorly, do not wait.
Later, see an allergy specialist to clarify the suspicion. This matters because an unverified penicillin allergy limits the choice of future antibiotics (Wurpts et al. 2020).
Frequently asked questions
What does a rash after antibiotics look like?
Usually red spots and small bumps, symmetrical on the trunk, arms and legs, sometimes merging, sometimes itchy. Wheals that move around and itch badly are a different form. Pictures on the internet help little; what matters are the warning signs and a medical assessment.
What should I do about a skin rash after antibiotics?
Watch for emergency signs and then call 112. Otherwise call the practice the same day, do not stop the antibiotic on your own, photograph the rash and keep the skin cool and leave it alone.
Should I stop the antibiotic?
Not on your own. Whether to continue, switch or stop is decided by the practice, which you call the same day. With emergency signs, call 112.
How long does the rash last?
An uncomplicated rash usually subsides within a week of stopping the medicine. It can also start 5 to 10 days after the end of the course.
Is a rash after antibiotics contagious?
A drug reaction is not. But if a viral infection is behind the rash, that may be contagious. The practice can clarify this.
Which ointment helps?
That is for the practice or pharmacy to decide, depending on the type of rash. Do not apply new creams or ointments on a hunch.
My child has a rash after amoxicillin. Is it an allergy?
Often not. In children, viruses are frequently behind it, and in one study the rash came back in only 6.8 % when the medicine was given again under supervision. An allergy work-up can clarify this.
Am I now allergic to penicillin?
Possibly, but not certainly. Have the suspicion entered in an allergy passport and tested later. Many suspected cases are not confirmed.
At forpeople
We have no product for a rash after medication, and as long as the skin is reacting, nothing new belongs on it. Whether and how to care for the skin afterwards is something to discuss with the practice.
Further reading: if your skin is simply dry after an infection, Dry skin after a cold or flu: causes and what helps can help. Which medicines can dry out the skin is covered in Dry skin from medication: causes and what you can do. Wheals with other triggers are explained in Hives (urticaria): wheals all over the body – triggers and what helps, individual dry patches in Dry patches on the skin: when harmless, when to see a doctor?. And if it was a reaction to a cosmetic: Reacting to a cosmetic: what to do, where to report, returns.
Sources
- Wurpts G, Aberer W, Dickel H et al. (2020): Guideline on diagnostic procedures for suspected hypersensitivity to beta-lactam antibiotics. Guideline of the DGAKI with AeDA, GPA, DKG, ÖGAI and PEG. Allergologie Select 4: 11–43. https://doi.org/10.5414/ALX02104E
- Caubet JC, Kaiser L, Lemaître B, Fellay B, Gervaix A, Eigenmann PA (2011): The role of penicillin in benign skin rashes in childhood: a prospective study based on drug rechallenge. Journal of Allergy and Clinical Immunology 127(1): 218–222. https://doi.org/10.1016/j.jaci.2010.08.025
- Chovel-Sella A, Ben Tov A, Lahav E et al. (2013): Incidence of rash after amoxicillin treatment in children with infectious mononucleosis. Pediatrics 131(5): e1424–e1427. https://doi.org/10.1542/peds.2012-1575
- DermNet: Drug eruptions (Dermatological emergencies). Created 2008, accessed on 30.10.2026. https://dermnetnz.org/cme/emergencies/drug-eruptions
- DermNet: Drug hypersensitivity syndrome (DRESS). Rademaker M (2004), updated by Oakley A, January 2016, accessed on 30.10.2026. https://dermnetnz.org/topics/drug-hypersensitivity-syndrome
- MSD Manual, consumer version (German): Stevens-Johnson-Syndrom (SJS) und toxische epidermale Nekrolyse (TEN). Benedetti J, reviewed May 2024, accessed on 30.10.2026. https://www.msdmanuals.com/de/heim/hauterkrankungen/überempfindlichkeitsreaktionen-und-reaktive-hauterkrankungen/stevens-johnson-syndrom-sjs-und-toxische-epidermale-nekrolyse-ten
- Ring J, Beyer K, Biedermann T et al. (2021): Guideline (S2k) on acute therapy and management of anaphylaxis: 2021 update. Allergo Journal International 30(1): 1–25. https://doi.org/10.1007/s40629-020-00158-y
- NHS: Side effects – Antibiotics. Last reviewed 11.11.2022, accessed on 30.10.2026. https://www.nhs.uk/conditions/antibiotics/side-effects/
