In adults 18 and older, the most common side effects with NEXIUM may include headache, diarrhea, nausea, gas, abdominal pain, constipation, and dry mouth In children 1 to 17 years of age, the most common side effects with NEXIUM may include headache, diarrhea, abdominal pain, nausea, and drowsiness Dangerous Side Effects of Long-Term Nexium Use Proton Pump Inhibitors like Nexium are among the most prescribed drugs in the US for treating heartburn, indigestion, acid reflux, gastritis, and peptic ulcers. Atrophic gastritis has been noted occasionally in gastric corpus biopsies from patients treated long-term with omeprazole, of which NEXIUM is an enantiomer. You can do some research online about Nexium and immune suppression and see what turns up. Google is a great search engine. I haven't found anything that indicates immune system suppression but there are a considerable number of side effects to careful about. Long-term usage of Nexium can also cause some other side effects, though these are more mild than some of the other side effects. Nexium can cause acne, dermatitis, a rash, abnormal urine, diarrhea that alternates with constipation. Along with its needed effects, esomeprazole (the active ingredient contained in Nexium) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. A 2006 study published in the Journal of the American Medical Association shows that long-term use of Nexium and other proton pump inhibitors increases the risk of hip fractures in people over 50. Using Nexium for a long period of time may increase the risk of inflammation of the stomach lining, according to the FDA. At least one study showed long term use of Nexium and other PPIs could also increase the risk of death. Long-term use of Nexium may cause deficiencies of some nutrients. Absorption of vitamin B12, iron and calcium is aided by stomach acid, so reducing acid production may be expected to interfere with their absorption.