I started to notice the red eyes and migraines when i was taking a proton pump inhibitor called Rabeprazole for gastric reflux. I was able to take supplements with steric acid and mag sterate before that point with no noticeable problems. I was even taking large doses of omega 3 at the time. I always knew it was correlated.
The low stomach acid hypothesis would mainly make sense for proteins, though. (but see below) Low stomach acid results in reduced pepsin secretion, thus less protein hydrolysis. Here is the second link you posted:
Clin Exp Allergy. 2009 Oct 7.
Suppression of gastric acid increases the risk of developing Immunoglobulin E-mediated drug hypersensitivity: human diclofenac sensitization and a murine sensitization model.
Riemer AB, Gruber S, Pali-Schöll I, Kinaciyan T, Untersmayr E, Jensen-Jarolim E.
Department of Pathophysiology, Division of General Dermatology, Medical University of Vienna, Vienna, Austria.
Summary Background Hypersensitivity reactions towards non-steroidal anti-inflammatory drugs (NSAID) are common, although true allergies are detectable only in a subgroup of patients. The current study was prompted by a case observation, where a patient experienced generalized urticaria following his second course of diclofenac and proton pump inhibitor medication, and was found to have diclofenac-specific IgE. During recent years, our group has been investigating the importance of gastric digestion in the development of food allergies, demonstrating anti-acid medication as a risk factor for sensitization against food proteins. Objective Here, we aimed to investigate whether the mechanism of food allergy induction described can also be causative in NSAID allergy, using diclofenac as a paradigm. Methods We subjected BALB/c mice to several oral immunization regimens modelled after the patient's medication intake. Diclofenac was applied with or without gastric acid suppression, in various doses, alone or covalently coupled to albumin, a protein abundant in gastric juices. Immune responses were assessed on the antibody level, and functionally examined by in vitro and in vivo crosslinking assays. Results Only mice receiving albumin-coupled diclofenac under gastric acid suppression developed anti-diclofenac IgG1 and IgE, whereas no immune responses were induced by the drug alone or without gastric acid suppression. Antibody induction was dose dependent with the group receiving the higher dose of the drug showing sustained anti-diclofenac titres. The antibodies induced triggered basophil degranulation in vitro and positive skin tests in vivo. Conclusion Gastric acid suppression was found to be a causative mechanism in the induction of IgE-mediated diclofenac allergy.
PMID: 19817752
The problem only occurred when the drug was covalently linked to a protein, something that they had to do in the lab before they administered it. I don't think this is evidence that low stomach acid would lead to a drug sensitivity. At least not in the general case. However, I just thought of a possible mechanism whereby mag stearate might be a problem under a low stomach acid condition: Because stearic acid is a weak acid, the hydrochloric acid in the stomach would be expected to protonate it, rendering it non-ionic. Although I wasn't able to find any data on this, I hypothesize that magnesium stearate might dissolve in stomach acid, yielding Mg+2 and stearic acid. While stearic acid is a common food component without the sort of chemical character that would cause immunogenicity, magnesium stearate is substantially different, and it's conceivable that an immune response to it could occur. If the normal metabolic fate of magnesium stearate was conversion to magnesium ion and stearic acid in the stomach, then low stomach acid might interfere with this process, leaving intact magnesium stearate. Still, I would expect that to be an insoluble substance that would just pass through the GI tract. But if it's there, then maybe the immune system could see it. This hypothesis hinges on what the actual metabolic fate of magnesium stearate is. If it doesn't normally dissolve in the stomach, then my hypothesis linking mag stearate sensitization to low stomach acid is shot to hell.