Diarrhea is a common complaint with sources from anxiety to food poisoning to a virus. It's usually treated with rest and a bland diet, and most cases clear up in less than a week. A swollen or puffy appearance can also come from several different causes, although when accompanied by diarrhea, the list shortens. Additionally, the symptoms may be unrelated. Your health care provider may choose to treat one or the other, to see if it resolves.
Allergies
An allergic reaction to a food source can cause both swelling and diarrhea. Allergies to shellfish or fruits or nuts will cause an initial reaction of swelling, tingling and puffiness in the face as the allergic reaction begins. As the body begins to digest the allergen, diarrhea is a common symptom. Allergies can change over the years, so even if you've never had a food allergy before, it's worth checking out as the source of both your swelling and diarrhea.
Medications
Prescription medications often have side effects that include swelling and diarrhea. For example, the commonly prescribed antibiotic amoxicillin lists diarrhea as a common side effect, and swelling as a rare but possible side effect, usually caused by an allergy to the medication. Niacin, prescribed by some health care providers for control of cholesterol, can cause both diarrhea and swelling of the face, although the condition is usually short-lived. And prednisone, a popularly prescribed steroid, can cause both swelling due to water retention, and diarrhea.
Celiac Disease
Celiac disease, the body's inability to process wheat gluten, has both a puffy face and diarrhea as symptoms. The puffiness is caused by water retention. Usually people notice the diarrhea first and the puffiness only after they get their diet under control and then ingest some wheat product unintentionally. Oftentimes these symptoms can seem intermittant depending on how sensitive the individual is to gluten.
