It most certainly is, and during menopause also. One of the main reasons is that hormonal changes alter the body's temperature, which is not beneficial to our own cells but which may make conditions a little more cosy for invading pathogens.
YES
yes
yes.
lower your immune system by not eating anything
yes it dose
No, bruise are not a normal occurrence from menstruation. It is possible to bruise slightly easier during this time due to being lower in iron.
Stress hormones such as cortisol can lower the immune system.
they probably have a lower immune system
The CD4 count is an indication of how healthy the immune system is. The lower your CD4 count, the less cells there are available to fight infection. This would indicate that the person's immune system is not functioning optimally.
Immune system - the antibody IgE (immunoglobulin E) specifically.
lower blood pressure and an enhanced immune system
No, eating healthier foods should increase your immune system and reduce the chance of you getting sick. Maybe your body is adjusting to the change and just needs a little while.