 [ Symptoms ] why did i have an adverse reaction after taking gas x [ Disease ] it is possible to have an adverse reaction to any medication many people think over the counter medications are somehow safer than prescription drugs this is not the case all drugs can and do cause adverse reactions in some people among the many possibilities any given person could have an adverse reaction to dyes in the product inert ingredients in the product such as fillers and binders or the active ingredient itself you do not say what symptoms you are interpreting as an adverse reaction  but in general if you take any kind of medication prescription or over the counter and experience a rash swelling of the lipstongueface or difficulty breathing you should seek medical treatment a rash alone does not necessarily warrant a trip to the emergency room but the other symptoms do also in general once you have experienced an adverse reaction to a drug you should never take it again if you have questions about any medications you take even over the counter ones you can always consult your health care provider or a pharmacist wishing you well