The culprit of the sneezing fit is the Trigeminal nerve. This is the largest of the 12 cranial nerves and is the main sensory nerve for the face and mucous membranes, amongst other things. It processes the feeling of touch and pain, as well as the action for chewing and biting. This nerve is a mixed sensory and motor nerve.
If the receptors of the Trigeminal nerve are ‘excited’ by touch, for example plucking the eyebrows, then a defence reaction in the form of sneezing happens.
So if your client’s Trigeminal nerve run close to the brow area then you’ll be lucky to complete the brown shaping without your client sneezing.
I have found that waxing the brows is less likely to cause sneezing, until you need to pluck that one brow hair that has escaped the wax. Paying extra attention by applying pressure and stretching the skin next to the hair to pluck also helps.
It is always a good idea to have a box of tissues at the ready…..