Another pill or two is very very low risk of any problem. Other brands are even stronger (as noted above).
But it is a live bacteria being introduced to the body. I read some studies that show a small percent of people, generally seriously ill people with indwelling catheters or acute pancreatis, have had adverse events and even death. This was especially true with the strain that was in Metaflor before they stopped seling it in the states. That E.choli strain showed some of the best results, and also had some record of a few linked deaths.
This is why some favor pre-biotics to manipulate gut flora instead of live bacteria.
But again, the risk is very very low, and even lower if you currently do not have any problems taking the brand.
from one article that said...
Safety of Probiotics
For most populations, probiotic consumption is considered
safe and complications rare. A review on the safety of
probiotics by Snydman points out that although case reports of
bacteremia and endocarditis (LGG) as well as cases of fungemia
(S boulardii) exist, epidemiologic evidence suggests that there is
no overall increase in population risk based on usage data?7
This position is substantiated by a recent US government commissioned
review panel report. As a caveat, however, a high
profile multicenter placebo controlled Dutch RCT examining
probiotic supplementation in severe acute pancreatitis found a
higher incidence of mesenteric ischemia and death in the treatment
group. This is the only trial to date to infer such a
relationship, but supports the concept that probiotics should
be avoided in critically ill patients. Indwelling central vein
catheters and perhaps cardiac valvular disease may be relative
contraindications.
Ciorba, M. A. (2012). A Gastroenterologist's Guide to Probiotics. Clinical Gastroenterology and Hepatology, 10(9), 960-968. doi: 10.1016/j.cgh.2012.03.024