Initial Posting: 5/21/2016    Last Update: 8/2/2017
Answer: Yes, certain ingredients in probiotic supplements can cause allergic reactions in sensitive individuals -- particularly individuals with milk or yeast allergies. Contamination with mold can also cause an allergic reaction (all probiotic products reviewed by ConsumerLab.com are tested for potential contamination with molds and/or pathogenic bacteria). Inulin, a prebiotic which is sometimes added to probiotic supplements, is also a potential allergen.
Allergens in probiotics are also suspected to cause, on very rare occasion, a serious condition known as eosinophilic syndrome.
For more details about allergic reactions to probiotics, as well as other possible adverse effects, see the Concerns and Cautionssection of the Probiotics and Kefirs Product Review, which includes tests and quality ratings of popular probiotic products. Also be sure to check and compare the ingredients in each tested product, as can be found in the Review's Ingredients Table.