The Food and Drug Administration (FDA) has not approved Benadryl, which contains the ... they may be more likely to experience severe side effects.

That means some supplement products may not contain what the label says ... due to an increased risk of side effects like constipation and dizziness. If you take Benadryl, avoid other sedating ...

Related: Benadryl for Dogs: Side Effects of Long-Term Use At normal doses ... be sure to read the label on the package. It should be 100% diphenhydramine, not Benadryl-D or any other product.