Most patients will experience little to no side effects of a hair transplant. Most, such as minor discomfort can be treated with either prescription or over the counter pain medications. It is common to feel a tightening of the area in the back of the head where the donor site was removed. This usually subsides within the first few days.
Depending on how well the patient adhered to the pre-operative instructions (such as avoiding vitamin C or aspirin), there may be some minimal swelling to the facial area. Most patients will be prescribed medication to prevent swelling so this side effect is much less common. However, if swelling does occur it usually only lasts for several days, is completely painless and can be alleviated with the use of ice and elevation of the head.
As the patient heals from the procedure they can experience moderate itching of the scalp. This is actually a good sign that the grafts are healing appropriately. The doctor will provide instructions as to when you may start shampooing and using a topical ointment to help with this condition.
As you can see there are minimal side effects to a surgical hair transplant and as with any other surgery the benefits far outweigh any temporary inconvenience.