Bee propolis

Propolis is a natural anticoagulant and may interact when taken in combination with thrombosis or blood cloths preventing, blood thinning anticoagulant drugs such as Warfarin (also known as Coumadin, Jantoven, Marevan, and Waran), Acenocoumarol, Phenprocoumon (branded as Marcoumar, Marcumar and Falithrom), Heparin, Phenindione, Dicumarol, Dicoumarol, Lipo-Hepin, Liquaemin, and herbs coumarin and licorice.
There have also been [...]

In general, propolis is safe to use. It is a non-toxic substance and will not cause irritation for most people.
However, like with other honey bee products, there are some people who are allergic to propolis.
You may be one of them if you are:

allergic to any bee product (pollen, honey, royal jelly),
allergic to bee stings,
an asthma [...]

While Bee Propolis showed to be very effective in the treatment of infertility associated with mild endometriosis, caution should be exercised during time of pregnancy and breast-feeding. It is advised to avoid Bee Products - Honey, Bee Pollen and Royal Jelly - during pregnancy.
The effects of Propolis during pregnancy and breast-feeding have not been sufficiently [...]