Can Wegovy cause hives? Yes, Wegovy (semaglutide) can cause hives in some individuals, though this reaction occurs relatively infrequently. Hives, medically termed urticaria, represent a hypersensitivity reaction characterised by raised, itchy welts on the skin. The UK product information for Wegovy specifically lists rash and urticaria as recognised adverse reactions. Wegovy is a GLP-1 receptor agonist licensed for weight management in adults with obesity or overweight with weight-related comorbidities. Whilst most patients tolerate the medication well, understanding potential allergic reactions and appropriate management is essential for safe treatment. This article examines the relationship between Wegovy and hives, including recognition, management, and when to seek medical attention.

Can Wegovy Cause Hives?

Yes, Wegovy (semaglutide) can cause hives in some individuals. Hives, medically termed urticaria, represent a hypersensitivity reaction that may occur with any medication, including GLP-1 receptor agonists like Wegovy. The UK product information for Wegovy specifically lists rash and urticaria as adverse reactions that can occur during treatment.

Wegovy is a prescription medication licensed for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with weight-related comorbidities. It works by mimicking the glucagon-like peptide-1 (GLP-1) hormone, which regulates appetite and food intake through actions on the brain's satiety centres. Administered as a once-weekly subcutaneous injection, Wegovy has demonstrated significant efficacy in clinical trials for weight reduction when combined with lifestyle modifications.

The incidence of skin reactions with Wegovy appears relatively low based on clinical trial data, but individual susceptibility varies considerably. It's important to note that hypersensitivity to semaglutide or any of the excipients is a contraindication to using Wegovy, and the medication should be discontinued if a serious hypersensitivity reaction occurs.

Patients experiencing hives whilst taking Wegovy should take this symptom seriously, as it may indicate an allergic response requiring medical assessment. Understanding the nature of this reaction and appropriate management steps is essential for patient safety and optimal treatment outcomes.

Understanding Hives as an Allergic Reaction to Wegovy

Hives manifest as raised, itchy welts on the skin that can vary in size and may appear anywhere on the body. These lesions typically have a pale centre with a red surrounding area and can migrate across the skin surface, appearing and disappearing within hours. The pathophysiology of drug-induced hives involves an immune-mediated response where the body's immune system identifies the medication or its components as foreign substances.

When Wegovy triggers an allergic reaction, mast cells in the skin release histamine and other inflammatory mediators. This cascade results in increased vascular permeability, causing fluid to leak into surrounding tissues and producing the characteristic raised, itchy wheals of urticaria. The reaction may be immediate (occurring within minutes to hours of injection) or delayed (developing days after administration).

Several factors may contribute to allergic reactions to Wegovy:

• Active ingredient sensitivity: Hypersensitivity to semaglutide itself may occur, though anti-drug antibodies are uncommon according to clinical studies

• Excipient reactions: The UK formulation contains inactive ingredients such as disodium phosphate dihydrate, sodium chloride, and pH adjusters, which could potentially trigger hypersensitivity in some individuals

• Injection site factors: Local reactions at the injection site are relatively common

• Previous allergies: While not well-established, patients with previous allergies to other medications should exercise caution and inform their healthcare provider

It is worth noting that no established association between Wegovy and chronic spontaneous urticaria (hives lasting more than six weeks without identifiable trigger) has been reported in the product information. Most medication-induced hives resolve relatively quickly once the causative agent is discontinued. However, any patient developing hives should undergo proper medical evaluation to confirm the diagnosis and exclude other potential causes, as urticaria can result from numerous triggers including infections, other medications, foods, and autoimmune conditions.

What to Do If You Develop Hives While Taking Wegovy

If you develop hives whilst taking Wegovy, prompt action is important to ensure your safety and determine the appropriate course of treatment. The management approach depends on the severity of symptoms and whether they indicate a localised reaction or a more serious systemic allergic response.

Steps to take:

• Hold your next dose of Wegovy until you have consulted with a healthcare professional

• Document the reaction: Note when the hives appeared in relation to your injection, their location, size, and any accompanying symptoms

• Take photographs if possible, as hives may resolve before your medical appointment

• Avoid scratching the affected areas, as this can worsen inflammation and potentially lead to skin damage or infection

Seek urgent medical attention (call 999 or attend A&E) if you experience:

• Difficulty breathing, wheezing, or throat tightness

• Swelling of the face, lips, tongue, or throat (angioedema)

• Dizziness, fainting, or rapid heartbeat

• Feeling very unwell or collapse

These symptoms may indicate anaphylaxis, a severe allergic reaction requiring immediate emergency treatment.

For mild to moderate hives without systemic symptoms, contact your GP or prescribing clinician promptly. If they are unavailable, contact NHS 111 for advice. Your healthcare provider may recommend oral antihistamines (such as cetirizine or loratadine) to alleviate itching and reduce the urticarial response whilst awaiting assessment.

Your clinician will need to determine whether Wegovy should be permanently discontinued or whether the reaction might have been coincidental. This decision involves careful consideration of the temporal relationship between medication administration and symptom onset, the presence of alternative explanations, and the overall benefit-risk profile for your individual circumstances. If a serious hypersensitivity reaction is confirmed, Wegovy should not be restarted, and you may be referred to allergy services for further assessment.

Other Skin Reactions Associated with Wegovy

Beyond hives, Wegovy can cause various other dermatological reactions, though most are mild and self-limiting. Understanding the spectrum of potential skin-related adverse effects helps patients distinguish between common, benign reactions and those requiring medical attention.

Injection site reactions are among the most frequently reported skin-related adverse effects with Wegovy. These localised responses may include:

• Redness (erythema) at the injection site

• Swelling or induration

• Itching or mild discomfort

• Bruising or haematoma formation

• Small lumps or nodules at the injection site

These reactions typically resolve spontaneously within a few days and can often be minimised by rotating injection sites between the abdomen, thigh, and upper arm as recommended in the Patient Information Leaflet. Proper injection technique, following the instructions provided with your medication, can reduce the incidence of local reactions.

Other skin manifestations that have been reported with semaglutide include:

• Pruritus (itching) without visible rash, which may be generalised or localised

• Rash: Various types of rash have been documented

• Alopecia (hair loss): Hair thinning is listed in the product information and may relate to rapid weight loss rather than a direct drug effect

• Skin changes related to weight loss: Significant weight reduction can lead to loose skin, changes in skin texture, and altered appearance

It is important to note that while serious skin reactions are not specifically listed in the Wegovy product information, any severe, blistering, or painful rash warrants immediate medical evaluation.

If you experience any suspected side effects, including skin reactions, while taking Wegovy, you can report them directly to the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk or search for 'MHRA Yellow Card' in the Google Play or Apple App Store. By reporting side effects, you can help provide more information on the safety of this medicine.

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