23 year old male had 7 colds already this year now another one. doctor did blood, urine and stool sample all good. i have stress, is that cause ?

Colds: If your doctor has done a work up for your frequent colds and serious conditions have v=been ruled out, them stress can diminish your immunity and make you susceptible to frequent colds. Please check your work environment, contacts and are they really colds or allergies ?

Depends: Did you contact an ill person each of those 7 times, have a 1 week illness with runny nose, changing from clear to thick secretions and residual cough, no fever? Perhaps what you call a cold, is something else. Fortunate for you, your physician has not found an underlying illness. Try and be accurate about your illness, and be clinically examined the next time around, to be sure.

Possibly: Some people are just more predisposed to infections and that may be the case for you. But you are right that stress can weaken the immune system, so make sure you are eating well, sleeping well, and remaining active and fit. Reassuringly it sounds like your doctor already addressed immune deficiency that may also contribute. Hopefully you stay healthy.

"Cold": Your frequent"colds" may in fact be due to allergies. An appointment with an allergist might resolve your problem