Side effects
Rash or itching on Zepbound: allergy or not?
The label counts a rash or itching as a hypersensitivity reaction, and says most of the ones seen in the trials were on the skin: 5 percent of people on Zepbound against 3 percent on placebo. Swelling of the face or throat, trouble breathing or a severe rash is a serious allergic reaction: stop and get help right away.
The Oolite team, from the FDA labels
Sources checked Oct 27, 2026
Published Nov 9, 2026
Updated Oct 27, 2026 · 2 min read
The short answer
The label counts a rash or itching as a hypersensitivity reaction, and says most of the ones seen in the trials were on the skin: 5 percent of people on Zepbound against 3 percent on placebo. Swelling of the face or throat, trouble breathing or a severe rash is a serious allergic reaction: stop and get help right away.
What the label says
The first page of the prescribing information puts them on the list of the most common side effects:
From the labelThe most common adverse reactions, reported in ≥5% of patients treated with ZEPBOUND are: nausea, diarrhea, vomiting, constipation, abdominal pain, dyspepsia, injection site reactions, fatigue, hypersensitivity reactions, eructation, hair loss, gastroesophageal reflux disease.
The side effects table in §6.1 gives the line: hypersensitivity reactions in 3 percent of people on placebo, and in 5 percent at 5 mg, 10 mg and 15 mg. The Medication Guide calls them "allergic reactions" in its list of the most common side effects.
The same section then says when they came:
From the labelIn a pool of Study 1 and 2, immediate hypersensitivity reactions (within one day after drug administration) occurred in 2.1% of ZEPBOUND-treated patients compared to 0.4% of placebo-treated patients, while non-immediate hypersensitivity reactions occurred in 3.5% of ZEPBOUND-treated patients compared to 2.7% of placebo-treated patients.
And what they looked like:
From the labelThe majority of the hypersensitivity reactions in trials were skin reactions (e.g., rash, itching).
Immediate or later, at the spot or elsewhere
Two lines of the label are easy to mix up. An injection site reaction stays where the needle went: redness, itching or swelling at the spot. A hypersensitivity reaction is counted on its own line, and in the trials it was mostly a rash or itching, sometimes within a day of the shot (immediate), more often later (non-immediate). The non-immediate ones were almost as frequent on placebo (2.7 against 3.5 percent); the immediate ones were the clearer difference (0.4 against 2.1 percent).
The label also links them to antibodies. Among people on Zepbound, hypersensitivity reactions were more frequent in those who developed antibodies against tirzepatide (6.2 percent) than in those who did not (3 percent).
When it is a serious allergic reaction
Severe reactions were rare in the trials, and the warnings section says so with a number:
From the labelThere have been postmarketing reports of serious hypersensitivity reactions (e.g., anaphylaxis, angioedema) in patients treated with tirzepatide. In a pool of two ZEPBOUND clinical studies for weight reduction (Studies 1 and 2), 0.1% of ZEPBOUND-treated patients had severe hypersensitivity reactions compared to no placebo-treated patients.
What it asks is plain:
From the labelIf hypersensitivity reactions occur, advise patients to promptly seek medical attention and discontinue use of ZEPBOUND.
The Medication Guide gives the signs in everyday words:
From the labelStop using ZEPBOUND and get medical help right away if you have any symptoms of a serious allergic reaction including:
swelling of your face, lips, tongue or throat; problems breathing or swallowing; a severe rash or itching; fainting or feeling dizzy; a very rapid heartbeat.
A milder rash that comes back after each shot, or itching that does not settle, is still worth a call to the prescriber, who decides what happens with the next dose.
Oolite's journal keeps side effects with the day they happened and the day of the shot, so the report for your prescriber shows whether a rash follows the injections.
Questions people ask
How common is a rash or itching on Zepbound?
In the two main trials, hypersensitivity reactions were reported by 5 percent of people at each dose (5, 10 and 15 mg) against 3 percent on placebo. The label says most of them were skin reactions, such as rash and itching.
Is a red, itchy spot where I injected the same thing?
The label counts it separately, as an injection site reaction, in 6 to 8 percent of people against 2 percent on placebo. A reaction that stays at the spot is that line; a rash elsewhere on the body is counted with hypersensitivity reactions.
Can I keep using Zepbound if I get a rash?
That is your prescriber's call, and it is worth calling. The label asks patients with a hypersensitivity reaction to seek medical attention promptly and to stop Zepbound, and the Medication Guide says not to use it after a serious allergic reaction to tirzepatide or its ingredients.
I had an allergic reaction to another GLP-1 medicine. Does that matter?
The label asks for caution in people with a history of angioedema or anaphylaxis with a GLP-1 receptor agonist, because it is not known whether they are more likely to react to Zepbound. Tell the prescriber before the first shot.
Sources
- Zepbound prescribing information, Eli Lilly, §4, §5.6, §6.1 and §6.2, revised 8/2026 · Table 1: hypersensitivity reactions 3 percent placebo, 5 percent at 5, 10 and 15 mg; immediate reactions 2.1 vs 0.4 percent, non-immediate 3.5 vs 2.7 percent; 6.2 vs 3 percent with and without anti-tirzepatide antibodies; most were skin reactions (rash, itching); severe hypersensitivity 0.1 percent vs none; postmarketing anaphylaxis and angioedema; seek medical attention and discontinue; caution after angioedema or anaphylaxis with another GLP-1 receptor agonist.
- Zepbound Medication Guide, Eli Lilly, ZEP-0010-MG-20260828 · Signs of a serious allergic reaction (swelling of the face, lips, tongue or throat; problems breathing or swallowing; severe rash or itching; fainting or feeling dizzy; very rapid heartbeat); do not use after a serious allergic reaction to tirzepatide; allergic reactions among the most common side effects.
Sources checked Oct 27, 2026. This page is information, not medical advice: read the medical disclaimer, and talk to your prescriber or pharmacist about your own treatment.
Written by
The Oolite team, from the FDA labels
We make Oolite. Every answer starts from the FDA prescribing information, quoted word for word, and is rewritten when a label changes.
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