Hello. Thank you for asking at HCM. I went through your son s history. I would like to know a few more details like - Does he have nose allergy symptoms (nasal congestion, running nose, sneezing)? Does he have skin allergy or any other allergy? Has he ever had wheezing? Did he any time required nebulization? Does he have anyone in family with allergies? Is he exposed to smoke? However, from your given history, I would like to make following suggestions to you: 1. In reply to your main question - montelukast s safety - Yes, it is considered one of the safest drugs for allergic children. Of course, it can cause side effects like nausea, vomiting, headache, but they are rare. Unless your son is not experiencing any of these side effects, he can take montelukast regularly for long period. Montelukast is an effective drug for both allergic rhinitis (nose symptoms) as well as allergic asthma/wheezing/cough. If it can control symptoms, it can avoid other drugs like inhaled corticosteroids. However, I would like to specify here that montelukast does not work on immune system basically. 2. Of course, allergy panel testing is expensive. There are other low-cost allergy testing available, but their quality is doubtful. So personally I would suggest that whenever you go for allergy testing, please choose the best quality testing. 3. Please avoid exposure to dusts, smokes and air pollution to him as much as possible. 4. Hemoglobin 9.6 is a concerned to me for his immune system. It is desirable to maintain hemoglobin around 13-14. Low hemoglobin levels predispose to repeated infections. 5. A healthy diet rich in vitamins and minerals (adequate amounts of green leafy vegetables, fruits, sprouts, etc) will be good for his immune system for long run. Hope above suggestions will be helpful to you and solve your query. Should you have any other query, please feel free to ask at HCM. Wish your son the best of the health. Thank you & Regards.