In many European countries, side effects have been reported in pets whose owners use transdermal oestrogen-containing medicinal products. The pets came into contact with or licked the area where the medicinal product was applied, usually the upper arm.
In some European countries (Sweden, Denmark, Germany, ...) dogs and cats showing hyperoestrogenism or high oestrogen levels in blood have been reported in recent years. The owner was treated with transdermal oestrogen-containing products.
The animals came into contact with these products by licking or by direct contact with the area where the product was applied. This was mostly at the level of the upper arm. The reported side effects were hair loss, signs of sexual activity (also after castration or sterilisation), development of mammary gland tissue and feminisation (development of female characteristics in a male animal).
Most leaflets for this type of medicinal product include the warning to prevent transmission of the product to other persons and children (and in rare cases, animals). For example, it is recommended for people to wash their hands after applying the product, to cover the application area and to wash the application area before contact with other people. However, should the product be transmitted to other persons, it is recommended to wash the contact area carefully and contact a doctor if necessary.
It is obvious that these warnings are also relevant for pets and that, in addition to skin contact, licking the product may also be a risk. Contact your veterinarian if required.