The Veterinary Medicines Directorate (VMD) has issued a warning today, June 11, to anyone using hormone replacement therapy (HRT) or testosterone replacement therapy (TRT). The alert is particularly aimed at individuals who have regular contact with animals, including pets like cats and dogs.
Pets are naturally curious and affectionate, often staying close to their owners. This makes accidental exposure to topical hormone products more common than many realize. Evidence indicates that pets may absorb oestrogen or testosterone by coming into contact with areas of human skin where hormone gels or creams have been applied.
Forearms are frequently recommended as an application site in prescribing guidelines, which increases the risk of direct contact during cuddling or stroking. These everyday behaviors can lead to unintended hormonal effects in pets—a risk many owners are unaware of.
Fortunately, the risk can be managed with simple adjustments. It is important not to stop any prescribed medication if your pet shows signs of hormone exposure.
What Are Topical Hormone Products?
Topical hormone products containing oestrogen and testosterone are human medicines applied to the skin as part of HRT and TRT. HRT gels and creams help manage menopause symptoms. TRT products are used to replace low testosterone levels, a condition known as hypogonadism. There is also a TRT product authorized for women with hypoactive sexual desire dysfunction (HSDD).
Signs of Accidental Hormone Exposure in Pets
Hormonal changes in pets caused by secondary exposure vary by the animal's sex and the hormone absorbed. Female pets, whether spayed or not, may show signs similar to being in heat, such as vaginal bleeding and a swollen vulva. In pregnant animals, exposure can cause birth defects. Male pets may develop swollen mammary glands or changes in testicular size.
Pets of any sex can experience hair loss, behavioral changes, increased attention from other animals, and reduced growth rates. Long-term exposure may lead to less common effects like bone marrow suppression.
How to Reduce Risk
To minimize secondary exposure to your pet, the VMD recommends:
- Keep pets away from skin areas where topical hormone products have been applied.
- Wash hands with soap and water after application.
- Cover the application site with clean clothing, such as a t-shirt, once the product has dried.
- Consult the Patient Information Leaflet or a doctor if concerned.
What Is the VMD Doing?
The VMD continuously monitors reports of suspected adverse events from both veterinary and human medicines, including accidental exposure. A statement on Gov.uk reads: "All cases are evaluated, and we perform statistical analysis to identify groups of reports that could indicate a problem. By sharing findings, the VMD supports vets and pet owners in making informed decisions."
How to Report an Adverse Event
If you notice an adverse event in an animal after potential exposure to a human hormone product, report it directly to the VMD’s adverse event reporting service. Human adverse reactions should be reported to the Medicines and Healthcare Products Regulatory Agency (MHRA) via the Yellow Card scheme.
