If Botox migration occurs within the first day (4-6hrs), why do adverse effects occur days later?

The adverse effects of botox is not so much form migrating outside the intended area hours later.  That is said to shift responsibility of the injector to you, the patient.  This is not accurate.  The migrating is due to how the injection is performed and occurs almost immediately at the time of treatment.  Very quickly, the fluid associated with the serivce is absorbed.  We recommend avoiding exercises immediately after treatment to reduce the risk of bruising.  Like all botulinum toxin effects, the effect does take a couple of days to reach maximal effect.

Migration refers to the product traveling and affecting an unintended muscle. This is not common, but if it occurs it's soon after injection . The effects of Botox, both good and bad, however are not seen for several days after injection. If Botox migrated on the first day its effects won't be seen until days after. Botox is considered in full effect 14 days after treatment.

Botox only starts acting after 3-4 days even where it is desired to act. The results start showing only after 7 days. So even if the Botox migrates to a wrong place, the results will start showing only after 4 -7 days.  Botox is temporary and starts loosing its effect after 6 months. In some cases, it can even lose effect as early as 3-4 months.