Will lateral Botox browlift cause fluid retention?

Thank you for this interesting question regarding Botox injections.
Botox treatment lateral to the sides of your eyes should not cause any swelling.
Rarely, Botox injections are done under the eye (under mid-pupil) to smooth lines.  This can cause slight puffiness if the tear area is affected.  This effect is temporary and will go away - usually with a few weeks.

Botox is commonly used to relax the upper outer portion of the obicularis oculi muscle allowing the outer portion of the brow to lift.  The levator palpebrae superioris muscle which lifts the upper eyelid lies inside the eyesocket.  While fairly rare, it is possible that a small amount of Botox can move or spread effecting the levator palpebrae superioris muscle causing or aggravating ptosis.  If ptosis occurs, it usually only lasts for 2-3 weeks.  Good luck, Dr. Z.

Botulinum toxin is effective in browlifting by temporarily weakening the brow depressor muscles. It should not cause water retention.