Testosterone gel: what happens if it rubs off on other people
A case that first appeared in a medical journal several years ago has recently resurfaced in the media, highlighting an unexpected risk of hormone therapies: a baby girl in Sweden developed unusually large genitals after lying on her father’s bare chest, accidentally exposed to his testosterone gel.
The incident is a reminder that hormone treatments, while safe when used correctly, can pose risks to others if proper precautions aren’t followed.
Testosterone is a powerful sex hormone that plays a crucial role in male development. In the early months of life, babies undergo rapid development, making their bodies, and hormones, extremely sensitive. Even small amounts of testosterone absorbed through the skin can affect a baby’s development, particularly with repeated exposure.
Get your news from actual experts, straight to your inbox. Sign up to our daily newsletter to receive all The Conversation UK’s latest coverage of news and research, from politics and business to the arts and sciences.
During “mini-puberty” – a short surge in hormone levels occurring a few months after birth – boys experience rising testosterone levels that help complete reproductive system development and prime it for adulthood. This process also influences brain development.
In girls, oestrogen rises slightly during this period, but testosterone remains very low. When a girl is exposed to external testosterone, such as from hormone gel, it can cause unexpected changes, including enlarged clitoris or fusion of the labia. This is precisely what occurred in the Swedish case.
Testosterone gels are commonly prescribed to treat men with low testosterone deficiency. The gel is typically applied once daily to clean, dry skin on the shoulders, upper arms or stomach. These alcohol-based gels help the hormone absorb into the skin.
While the gel dries within minutes, residue can remain on the skin for an hour or two after application. If someone touches the treated area too soon, or rests directly on it, they can inadvertently absorb some of the hormone. This risk is particularly significant for babies and children, whose thinner, more absorbent skin and developing bodies make them more vulnerable.
Testosterone gels are also increasingly used off-label in women to treat menopause symptoms (such as low libido, low mood and fatigue) and at around one-tenth of the dose given to men. This lower dose is achieved by applying a smaller amount of the same male product — this time to the lower abdomen, buttocks or outer thighs.
This means there’s much less hormone overall, but incidental exposure from women is also possible, for example, when holding a child soon after application.
Some perspective
While stories like this understandably cause concern, it’s crucial to understand the actual risk level. In the UK, around 50,000 to 100,000 people are prescribed testosterone on the NHS, with gel formulations popular due to their ease of application. If accidental exposure were common, we would see far more cases than the small number reported in medical journals.
The instructions accompanying these gels are clear: apply only to specified areas, wash hands immediately, cover the skin once dry and avoid close skin contact for several hours. When these guidelines are followed, transfer is very unlikely.
In the case of the Swedish child, when the father stopped resting the baby on his bare chest, the genital changes reversed over time. This pattern holds true for other reported cases – if exposure stops early, many effects can fade naturally.
However, in more severe or prolonged cases, children may need medical treatment. This could include hormonal tests, continued monitoring, anti-hormone treatment, or even surgery if physical changes don’t resolve. Early intervention is key, making it essential to consult a doctor if there’s any concern.
For those with babies, young children, or pregnant partners at home, the solution is straightforward planning. Apply the gel when you won’t be in direct contact immediately afterwards, or consider alternative application methods such as injections, skin patches, or tablets (available in the US), which carry lower risks of unintentional exposure to others.
This case serves as a valuable reminder that testosterone therapy, like all medications, comes with responsibilities. When used properly, it’s an effective treatment for men with diagnosed testosterone deficiency, improving sexual function and mood, with evidence suggesting it can also support muscle mass, bone health, and metabolism.
There is no need to fear these treatments, but if you are prescribed this medication, use it responsibly and follow the instructions carefully.
Daniel Kelly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.