Hi thanks for asking us... You have history of seasonal allergy... So this time your child might also have allergic or viral infection of respiratory tract ... So it might be URTI... Investigate your case with CBC to look for lymphocytosis or eosinophilia that suggestive viral or allergic infection respectively.... Give your child decongestent like Fexofenedine or benadryl like drug... Steam inhalation three times a day... Give him hot water to drink ... Avoid excess spicy foods and oily foods ... It is better for avoiding swimming at least week as your child having seasonal allergy so cold water in swimming pool might increase your problem.... Give him one tsp turmeric powder in hot milk .... If you are living in cold weather room humidifier can be used .... If symptoms increasing than digital chest x ray needed for further work up ..... Consult physician with keeping this in mind ... Take care .....