Do allergies cause constipation

Sometimes. Coeliac disease, where people are allergic to gluten, can result in constipation. However in this case, other symptoms will also be prevalent such as frequent stomach pain and/or mouth ulcers/chronic anemia. There is also the possibility of a dairy allergy causing constipation, but again other symptoms will also be seen, such as stomach pain, skin rashes or eczema. In any case, having constipation is not an adequate basis to diagnose an allergy without further investigation.

Non-food Allergies (e.g hayfever or pet allergies) will not result in constipation.