Why is it that when the Christmas Season approaches, people also start going down with the colds? Ear infections, pneumonia and allergy is also prevalent nowadays.
The only real defense is to eat healthy and live a healthy lifestyle. Enough rest and sleep and stress management is key.
Fortifying yourself with Vitamin C or malunggay capsules will also help. For the highly allergic, maybe some antibodies shots is called for. Also, you may have to change your humidifier filters and get your air conditioning units cleaned.
But do enjoy the outdoors. Staying inside does not really help colds and allergies. Do avoid crowds though as much as you can while you're still down so you won't catch more opportunistic infections.