Shyness is a common occurrence linked to specific situations such as becoming a bit tense increased heart rate and uneven breathing before giving a speech. From a health standpoint shyness is not an illness.
Essentially, stress lowers our body’s resistance to viruses, bacteria, and disease as well as raising blood pressure. These factors are magnified in “shy” people as they have a tendency to be under more stress when they have to be social.
The following website might be of interest to you.
People who are socially inhibited are more vulnerable to viral infections, suggests a research conducted at the University of California.
In the studies conducted on animals, scientists have found that gregarious people (social),have lymph nodes more active in protecting the body than those shy.
Lymph nodes are part of the body's immune system and help destroy pathogens such as bacteria, viruses and common colds.