It is customary to refrain from haircutting during the Omer period, until the 34th day of the Omer (according to Sephardic custom). Preferably, one should also refrain from shaving during this period, though there is room to be lenient in this regard for those who need to shave for professional reasons and the like. However, even those who, for whatever reason, shave during the Omer should refrain from trimming their sideburns and any other hair on their body. The leniency applies to facial hair, but not to other hair, so they should not cut their sideburns or any other hair.
The exception to this rule is a case where ones moustache is overgrown and interferes with his eating. A person in this case may trim his moustache during the Omer. This applies even to those who refrain from shaving during the Omer; they may trim their moustache if it has grown to the point where it interferes with eating.
It should be noted that the custom to refrain from haircutting during the Omer applies only to the customary modes of hair removal. People occasionally play with their hair, eyebrows or beards and pluck hairs. This is permissible during the Omer, since the custom relates only to the usual methods of haircutting.
