Hello everyone! Such a question, about small children and air conditio…

Hello everyone! Such a question, about small children and air conditioners, my son is almost 1.10 years old, last year respectively 9-10 months, in summer was constantly conditioner, didn't get sick once, we usually set it at 20-22 degrees... this year already 3 days we are being treated ?‍♀️ why so? We have an apartment sunny and stuffy, without conditioner, can you tell me what to do ??‍♀️