My baby is 18 months old. has had a runny/blocked nose and cough for 7 weeks now. i have used texa syrup, avamys nasal spray, rinex, coryx, humidifier, nebulise, nose sucking, saline spray. it is not getting better. allergy or something else?

Yes possible Allergy. Other possible causes: Asthma (especially if night cough and if parent has asthma), Chronic sinus infection, foreign body or Adenoid hypertrophy, among others. The pediatric provider or specialist can help with a full history and other studies such as allergy tests, chest imaging, sweat tests if necessary. With this work up, the right treatment can help symptoms!