I think my husband is allergic to avacado ..before...

Treatmen of stomach pain:
Stomach pain is one of the most common medical problems in the world, and usually it can be treated by conservative management as avoiding stress, getting enough water daily, avoiding salts, avoiding smoking.
And if there is no response, it can be treated by:

• Omeprazole 20 mg twice daily
• If there is H.pylori infection, you can take augmentin 500 mg three times daily and flagyl 500 mg three times daily

Diagnosis of the cause of stomach pain:
It depends on the clinical examination by a gastroenterologist and investigations as H.pylori for bacterial infection, upper endoscope to detect gastritis and to rule out hiatus hernia and taking biopsy if possible, ALT,AST for liver diseases, amylase for pancreatic problems, billirubin for gallbladder problems.
Causes of stomach pain:
It may be due to:

• Stress and anxiety
• Gastritis
• Drinking too much caffiene
• pylori infection
• Smoking
• Liver disease
• Gallbladder disease
• Pancreas disease...etc