Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes mellitus, with proven efficacy in glycaemic control and weight reduction. Whilst gastrointestinal side effects are well documented, some patients have questioned whether Mounjaro causes eczema or worsens existing skin conditions. Although current clinical data do not establish a direct causal link between tirzepatide and eczema (atopic dermatitis), skin reactions including injection site irritation, rash, and pruritus have been reported. Understanding the potential for dermatological changes, recognising symptoms, and knowing when to seek medical advice are essential for safe and effective use of this medication.

What Is Mounjaro and How Does It Work?

Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus. Tirzepatide is also available under the brand name Zepbound for weight management in adults with obesity or overweight with weight-related comorbidities, though NHS access is restricted by NICE guidance (TA1026). It belongs to a novel class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. By activating both GIP and GLP-1 receptors, tirzepatide enhances insulin secretion in response to meals, suppresses glucagon release, slows gastric emptying, and reduces appetite—collectively improving glycaemic control and promoting weight loss.

The medication is administered once weekly via subcutaneous injection, typically in the abdomen, thigh, or upper arm. Tirzepatide's dual-agonist mechanism distinguishes it from single GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and liraglutide (Victoza, Saxenda). Clinical trials (SURPASS and SURMOUNT programmes) have demonstrated significant reductions in HbA1c levels and body weight, making Mounjaro an effective option for patients who have not achieved adequate control with other antidiabetic therapies.

Common side effects of Mounjaro predominantly involve the gastrointestinal system and include nausea, vomiting, diarrhoea, constipation, and abdominal discomfort. These effects are usually mild to moderate and tend to diminish over time as the body adjusts to the medication. When used with insulin or sulfonylureas, there is an increased risk of hypoglycaemia. As with any pharmaceutical agent, Mounjaro may also cause less common adverse reactions, including dermatological manifestations. Understanding the full spectrum of potential side effects—including skin-related changes—is essential for both patients and healthcare professionals to ensure safe and effective use of this medication.

Recognising Skin Side Effects While Taking Mounjaro

While gastrointestinal symptoms are the most frequently reported adverse effects of Mounjaro, skin reactions have also been documented, though they occur less commonly. According to the Summary of Product Characteristics (SmPC), documented skin-related adverse reactions include injection site reactions (such as redness, itching, swelling, or bruising), rash, pruritus (itching), and urticaria (hives). Rare but serious hypersensitivity reactions, including anaphylaxis and angioedema, have also been reported. It is important to note that there is no official, established causal link between Mounjaro and the development or exacerbation of eczema (atopic dermatitis) based on current clinical trial data and post-marketing surveillance.

However, some patients have reported experiencing eczema-like symptoms—such as dry, inflamed, itchy patches of skin—after starting Mounjaro. These reports may reflect:

• Coincidental timing: Eczema is a common chronic inflammatory skin condition affecting a significant proportion of the UK population, and flare-ups can occur independently of medication use.

• Injection site reactions: Localised skin irritation at injection sites may occasionally resemble eczematous changes, particularly if the skin barrier is compromised.

• Individual susceptibility: Some patients may have pre-existing skin conditions that become more noticeable during treatment.

• Changes in hydration: Weight loss may affect skin hydration in some individuals.

Patients should be vigilant for new or worsening skin symptoms, including persistent itching, redness, scaling, weeping, or thickened skin patches. Documenting the timing, location, and severity of these symptoms can assist healthcare professionals in determining whether they are related to Mounjaro or represent an independent dermatological condition requiring separate management. If you develop widespread hives, facial swelling, or difficulty breathing, seek immediate medical attention as these may indicate a serious allergic reaction.

Managing Eczema Symptoms During Mounjaro Treatment

If you develop eczema-like symptoms while taking Mounjaro, several practical measures can help manage discomfort and support skin health. It is important to maintain a consistent skincare routine that focuses on restoring and protecting the skin barrier, which is often compromised in eczema.

Emollients and moisturisers form the cornerstone of eczema management. Apply generous amounts of a suitable emollient—such as emulsifying ointment, fragrance-free moisturisers (e.g., Diprobase, Cetraben, Epaderm), or ointments like 50:50 liquid paraffin/white soft paraffin—at least twice daily and after bathing. Ointments are generally more effective than creams for very dry or inflamed skin. Avoid products containing potential irritants such as fragrances, sodium lauryl sulphate (SLS), or alcohol. Note that aqueous cream containing SLS should not be used as a leave-on moisturiser as it may irritate the skin.

Topical corticosteroids may be necessary for managing active eczema flares. Mild-to-moderate potency corticosteroids (e.g., hydrocortisone 1% for facial/flexural areas, or clobetasone butyrate 0.05% for body sites) can reduce inflammation and itching. Apply a thin layer to affected areas once or twice daily, as advised by your GP or dermatologist. For adults, use the fingertip unit guide: one fingertip unit (the amount from the tip to the first crease of the index finger) covers an area twice the size of an adult's palm. Apply emollients first, then wait about 30 minutes before applying the steroid. Short courses (typically 5-14 days) are usually sufficient for flares. Avoid prolonged use without medical supervision.

Additional strategies include:

• Avoiding triggers: Identify and minimise exposure to known eczema triggers such as harsh soaps, detergents, wool fabrics, extreme temperatures, and stress.

• Bathing practices: Use lukewarm (not hot) water and soap substitutes. Pat skin dry gently and apply emollient immediately afterwards to lock in moisture.

• Injection site care: Rotate injection sites as recommended, ensure the skin is clean and dry before injecting, and apply emollient around (but not directly on) the injection site if irritation occurs.

If symptoms persist despite these measures, or if you are uncertain whether your skin changes are related to Mounjaro, consult your GP or diabetes specialist nurse for further assessment and tailored advice. Do not stop taking Mounjaro without discussing with your healthcare provider.

When to Seek Medical Advice About Skin Changes

While mild skin reactions are often manageable with self-care measures, certain symptoms warrant prompt medical evaluation. You should contact your GP, diabetes specialist nurse, or pharmacist if you experience:

• Severe or worsening eczema: Extensive areas of inflamed, weeping, or crusted skin that do not improve with emollients and over-the-counter treatments.

• Signs of infection: Increased pain, warmth, swelling, pus, or yellow crusting on affected skin, which may indicate secondary bacterial infection (commonly Staphylococcus aureus) requiring antibiotic therapy.

• Eczema herpeticum: Clusters of painful, punched-out lesions or blisters, often with fever, which requires same-day assessment as this herpes simplex infection can spread rapidly and become serious.

• Systemic symptoms: Fever, malaise, or feeling generally unwell alongside skin changes, which could suggest a more serious reaction.

• Severe injection site reactions: Persistent redness, swelling, or pain at injection sites that does not resolve within a few days, or the development of nodules or abscesses.

• Allergic reactions: Symptoms such as widespread rash, hives (urticaria), facial swelling, difficulty breathing, or dizziness, which may indicate anaphylaxis—a medical emergency requiring immediate attention (call 999).

Your healthcare provider will assess whether your skin symptoms are likely related to Mounjaro or represent a separate dermatological condition. In some cases, referral to a dermatologist may be appropriate for specialist evaluation and management. If a clear link between Mounjaro and your skin symptoms is established, your doctor will discuss the risks and benefits of continuing treatment versus switching to an alternative medication.

If you cannot reach your GP and need urgent advice, contact NHS 111. For suspected side effects of Mounjaro, you can report these via the MHRA Yellow Card Scheme (https://yellowcard.mhra.gov.uk), which helps identify previously unrecognised adverse reactions. By communicating openly about any skin changes or other concerns, you contribute to the safe use of Mounjaro and help ensure that you receive the most appropriate and effective treatment for your individual needs.

Frequently Asked Questions