It depends on several factors, among them the quality of the recipient’s capillary bed, the vascularisation and nutritional contribution the bed can provide, as well as several factors that we will list down below:
The area receiving the graft must be in optimal conditions, it must not have active infectious processes and its vascularisation must be adequate, so that it can nourish the grafted tissue.
Follicular trauma, either due to pulling, stretching, bending or crushing, is enough to diminish follicular growth rate. The deterioration phenomenon can be observed with an electronic microscope. Just a slight touch on the bulb can cause a decrease in growth from 35 to 64%.
There are nowadays several types of means for follicular conservation, among them:
Only 3 minutes are enough for the follicles to begin to deteriorate, thus decreasing follicular growth. There is greater deterioration in the follicular units of 1 hair, than in those of 2, 3 and 4 hairs.
High density in procedures with more than 50 follicles/cm2 has a low survival rate in relation to others with lower density. This phenomenon occurs due to the effect of ischemia-reperfusion.
Cold acts as a protective factor against physical damage. A temperature of 4° C (39° F) is ideal to keep the follicles viable with a better survival rate.
In 1992, Dr Bob Limmer conducted a study with 200 follicular units with different periods of time outside the body and he found the following:
| HOURS | % SURVIVAL |
| 2 | 95% |
| 4 | 90% |
| 6 | 88% |
| 8 | 83% |
| 24 | 79% |
| 48 | 54% |