Kefir is well tolerated by most. However, there are some things to bear in mind when adding kefir into your diet.
For example, fermented food and drinks tend to have a minute alcohol content. Although extremely low this can be an issue for those who do not tolerate alcohol well.
Additionally, the beneficial bacteria found in fermented products such as kefir can cause minor stomach upsets in some people. These bacteria also make kefir unsuitable for those with immune system disorders.