By "allergies" I mean any allergies, whether it's hay fever or breaking out in hives from shellfish. I personally do not believe in "subtle" food allergies, I believe that true food allergies almost always produce clear symptoms such as swollen lips or hives. Digestive problems alone usually isn't a sign of food allergy, it's an intolerance, which is different.
Now back to the point:
Okay, asthma and multiple bouts of vomiting, now this is starting to make a bit more sense.
Repeated vomiting can actually damage the esophagus and lead to acid reflux that goes on for a while. A few weeks of treatment with PPI's can usually resolve this, although not always. Further, PPIs can become less effective after a few months of use, because the body develops tolerance.
Asthma and acid reflux interact in some pretty awful ways. (I also have both now!)
Bouts of acid reflux can trigger asthma symptoms if the acid tickles the lungs.
Asthma can also cause acid reflux, because coughing and straining to breathe can upset the digestion.
Asthma MEDICINES can also cause acid reflux, particularly antihistamines such as Zyrtec and beta-agonists such as albuterol or salmeterol. Beta-agonists are literal lifesavers for asthma patients, do not stop using them unless the doctor okays it, but keep in mind they may make the acid reflux harder to control.
A diet low in saturated fat may help control both conditions.
May I ask what exactly he's taking? I presume the inhalers are a rescue inhaler and a daily steroid?