* Brewer's yeast seems safe for most people when used short-term. It can cause headache, stomach discomfort, and gas (flatulence).
*Autism : Many children on the autism spectrum have trouble with yeast in general and many physicians have used antifungals to combat the overgrowth of yeast in autistic children. In fact, some physicians speculate that the yeast in bread is actually more of a concern – so they recommend a gluten-free, yeast free diet. Keep in mind, even though yeast may be helpful for some conditions, autism is not considered to be one of them.
* Pyretic effect : Brewer's yeast is a potent inducer of fever, sickness behavior and inflammation within the brain.
*Pregnancy and breast-feeding: Not enough is known about the use of brewer’s yeast during pregnancy and breast-feeding. Stay on the safe side and avoid use.
*Yeast allergy: People who are allergic or sensitive to yeast might experience itching and swelling.