Thanks for your question and concern about your friend. If he is allergic to most pain killers, it is better to prevent occasions which make him taking medications for killing pain. Allowing enough sleeping hours can also help. Stress giving foods including wine, cheese and chocolates should be best avoided. Using a good pillow also will help in relieving stress and tension. Natural medications such as yoga and meditation also help. Jogging and simple walking fo about 30 minutes or more also will help in reducing stress and related problems.