Redness on Forehead a Few Weeks Later As a Result of Botox--am I Having an Allergic Reaction?

Regardless of the area injected, Botox does not cause redness. If the injections caused a delayed bruise (one or two days) the redness from the bruising (usually purple) would go away totally in three weeks. It is highly unlikely after Botox injections that the needles caused some proliferation of capillaries (tiny blood vessels). See your doctor to determine what is the redness from. 

Some people can get seborrhea, not from injections, but for reasons we don't understand, and the red flaking skin is often near the eyebrows. 

The information provided in Dr. Shelton's answer is for educational purposes only and is not intended to constitute medical advice.  The information provided should not be relied upon as a substitute for consultations with a qualified health professional who may be familiar with your individual medical needs.

You're not likely having a reaction to the Botox itself, but possibly something topical used during the procedure. I would suggest following up with your provider to inquire about what was used during your treatment and ensure they don't use it again. You also might have a consult with a reputable dermatologist for a more thorough assessment.

Typically after Botox injections, you may have some redness and a little swelling (similar to a mosquito bite) for about half an hour.  After that it would be very unusual to have any prolonged redness.  Without seeing a picture or seeing you in person, it is impossible to give you any specific advice.

 

Good luck.