Hi Thanks for posting on HCM You gain weight when you eat more than you work, that is, energy from food you eat is more than energy you use for your daily activities.The excess energy will be stored as fats in adipose tissues and proteins in muscle.The easiest way to maintain good weight is to control diet and exercise regularly.Happy weight gain is not your concern for now. As for the allergy problem, the best treatment of allergy is to avoid the allergens if they can be identified.I will suggest you avoid all that trigger your symptoms.Since it may be difficult to identify all allergens, you may try the following when symptoms start: -Take an anti-histamine like loratadine -A steroidal anti-inflammatory like dexamethasone but not for long. Hope this will help you Best regards