It is possible that exercise induced allergies are aggravated due to heat. It is possible that a person may have a reaction to heat, this may be something called as "cholinergic urticaria" or "dysautonomia". You must talk to your doctor if you think its the heat which causes it. A firm diagnosis is essential specially in light of the unfortunate loss of your brother.
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Please I have been experiencing nagging cough severely at nights and sometimes during the day.Sometimes it is associated with sputum in my blood. I have taken x-ray and skin test TB test but the results were ok. Please what could this be