Patients should avoid propolis if they have had allergic/hypersensitivity reactions to propolis, Populus nigra L. (black poplar), poplar bud, bee stings/bee products (including honey), or Balsam of Peru. There are multiple reports of swelling, fluid collection, redness, burning, eczema, swelling, fever, and other allergic reactions (including a severe allergic reaction called anaphylaxis) with repeated use of propolis on the skin. Propolis has been linked to several cases of contact dermatitis in beekeepers. Allergic contact stomatitis has been associated with the therapeutic use of propolis.

The safety of propolis has not been thoroughly studied. Although there are several case reports of allergic reactions to propolis, it is generally believed to be well tolerated in most adults. Allergic reactions may cause swelling, redness, eczema, or fever. Propolis may irritate the skin and may cause burning, peeling lips, irritation, lesions, itching, swelling, psoriasis, or eczema. Case reports of irritation in and around the mouth have occurred after use of propolis lozenges or extract taken by mouth.

Toxicity data for propolis are limited. Early studies have found propolis to be relatively non-toxic. There has been one report of kidney failure with the ingestion of propolis that improved upon discontinuing therapy and worsened with re-exposure.

There is not enough scientific evidence to recommend the use of propolis during pregnancy or breastfeeding. Many tinctures contain high levels of alcohol and should be avoided during pregnancy.

Propolis may protect against male infertility, although this use has not been thoroughly studied.

There is no proven effective medicinal dose of propolis. However, a wide range of doses has been studied for various conditions. A 5% ointment/cream/aqueous solution of propolis applied in the form of vaginal dressings/douche daily has been used for 7-10 days for acute cervicitis or vaginitis. To treat recurring canker sores, a dose of 500 milligrams of propolis has been taken orally daily. A dose of 10 milliliters of 0.2% to 10% propolis ethanol extract mouthwash (swished in the mouth for 60-90 seconds, then spit out) has been used once or twice daily for dental plaque. For genital herpes simplex virus infection, a 3% propolis skin cream (made from 75-85% concentrated propolis extract) has been applied to the skin four times daily for 10 days. In cases of cervical or vaginal lesions, the same amount of ointment has been applied to the tip of a tampon and inserted vaginally four times daily for 10 days. Safety and effectiveness have not been established.

A dose of two 250 milligram propolis capsules has been taken by mouth three times daily for three days to treat bacteria in the urine. A 20-30% propolis extract has been taken by mouth for five days to treat giardiasis (milligram dosing not clearly described). Safety and effectiveness have not been established.

A dose of 2 milliliters of aqueous propolis extract has been injected every 14 days for up to seven months for Legg-Calve-Perthes disease/avascular necrosis of the hip. Effectiveness and safety have not been established, and dosing should only be under the supervision of a qualified healthcare professional.

A 10% ethanol extract of propolis has been taken by mouth over five days for giardiasis (milligram dosing not established). Note that ethanol (alcohol) preparations should be used cautiously in children. Safety and effectiveness have not been established.

A 0.5 milliliter propolis nasal spray (Nivcrisol®) has been used once weekly for five months in preschool children (average age six years) and school-age children (mean age nine years) over a five-month period to treat respiratory infections. Safety and effectiveness have not been established. An herbal preparation (Chizukit) containing 50 milligrams per milliliter (mg/mL) of echinacea, 50 mg/mL of propolis, and 10 mg/mL of vitamin C, or placebo (5 milliliters and 7.5 milliliters twice daily for ages 1-3 years and 4-5 years, respectively) has been used for 12 weeks. Currently there is not enough scientific evidence to support the use of propolis for respiratory tract infections.

Many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).

Propolis may produce additive effects when taken with antimicrobial drugs.

Propolis may interact with the following: anticoagulants, H. pylori agents, antibiotics, anti-cancer agents (antineoplastics), antifungals, anti-inflammatories, infertility agents, anti-HIV agents (antiretrovirals), immunosuppressants, and osteoporosis agents.

Balsam of Peru and propolis are both known to cause allergic sensitization in some people and have multiple compounds in common, such as benzyl benzoate, benzyl cinnamate, benzyl alcohol, benzoic acid, cinnamic acid, caffeic acid, cinnamic alcohol, and vinallin. An increased risk of allergic sensitization may occur if both products are used together.

Propolis may interact with the following herbs and supplements: anticoagulants (such as coumarin and licorice), antibacterials, anti-cancer agents (antineoplastics), antifungals, anti-inflammatories, antioxidants, fertility agents, anti-HIV agents, immunostimulants, immunosuppressants, and osteoporosis agents.