When you consume a probiotic for the first time you may experience some side effects in the first few days or weeks due to the changes in the gut microbiome and whilst your body gets used to these changes. These side effects won’t happen for everyone but might include:
- gas and bloating (1) (2) (3) (6) – you may wish to stop the probiotic and contact your healthcare provider if this goes on for too long (1) (3). They may suggest switching to another probiotic (2)
- if you are taking a yeast-based probiotic, you may experience constipation and increased thirst (1)
- some probiotic rich foods such as yogurt, sauerkraut and kimchi contain amines such histamine, tyramine, tryptamine and phenylethylamine, which can excite the nervous system and alter blood flow resulting in headaches in sensitive individuals (1) (3)
- some probiotic strains increase histamine levels. Histamine is normally broken down in the gut by an enzyme called diamine oxidase (DAO), but those with histamine intolerance (4) don’t produce enough DAO. In these cases, excess histamine is absorbed through the gut lining into the blood stream causing allergy type symptoms. (1) It may be wise for those with histamine intolerance (4) to avoid histamine forming probiotics
- probiotic product labels must be read carefully by those with allergies since products may contain allergens such as dairy, egg, gluten or soy (1) (2). Two participants who took probiotics for IBS in a 2018 study experienced skin rashes, so it worth checking the products for allergens (2). Anyone experiencing an allergic reaction to a probiotic product should stop the product immediately and seek medical help if the reaction is severe (2)
- some probiotics can cause allergic reactions in themselves. Multiple studies found L. rhamnosus GG. caused allergic reactions in some people. L. acidophilus LAVRI-A1 was linked with allergic reactions in infants younger than 12 months in a study. Another study found probiotics caused asthma and hay fever symptoms in some children (3)
- some probiotics come with prebiotics such as lactulose, inulin and various oligosaccharides (1). Many people with IBS suffer from dysbiosis – a dominance of bad bugs in the gut, which contribute to IBS symptoms. Prebiotics not only feed good gut bacteria, they also feed the bad bugs. IBS suffers may find it beneficial to initially take probiotics without prebiotics in them, to allow the probiotics to crowd out the bad bugs to reduce their numbers. Otherwise those with IBS may suffer excessive gas and bloating from these products without the bad bugs being brought under control first
- in rare cases, such as those with severe illnesses (2), going through chemotherapy (5) (3), suppressed immune systems, long hospital stays, venous catheters or had recent surgery, probiotics may create a risk for infection, which should respond to antibiotics or antifungals (1) (except potentially in the case of spore based probiotics). In very rare cases this can lead to death (1). Those with severe acute pancreatitis are advised not to take probiotics according to research due to the associated increase risk in death (1). However, as an example, the risk from infection with Lactobacilli bacteria across the general population is estimated to be one in one million people and one in 5.6 million users from yeast-based probiotics (1). Anyone who may be at risk from probiotics should discuss their use with a doctor in the first instance (2)
- anyone with SIBO may need to avoid probiotics since probiotics will add more bacteria on top of the excess of bacteria in the small intestine (2)
- currently under research is whether some probiotics can transfer antibiotic resistant genes to bad bugs in your gut (3). To guard against this always source probiotics from trusted, reputable manufacturers who will systematically test commercial probiotics stains for the presence of antibiotic resistance (2)
You can reduce the likelihood of side effects by starting with a lower dose and increasing to a full dose over a few weeks (1). If the probiotic is in capsule form you could carefully open the capsule in order to consume part of it and close the capsule again.
Studies have shown that probiotics are safe to take for most people (3).
IBS Researcher 