Is it unusual for a patient to have a reaction to the stitches? Is there a way to test if a person will be allergic to them?

Unfortunately, some patients do experience reactions to sutures that can result in inflammation, localized pustules (like pimples around the suture), or discomfort and sensitivity. The sutures eventually dissolve, but may cause irritation before they dissolve. At times, suture knots can be cut out by the surgeon to improve this situation. There is no way to know in advance who might react poorly to a particular suture, but fortunately most patients heal without such problems. If a poor scar does result, which is not usually the case, the scar can generally be revised and improved later.

There is no way of predicting whether you will have any issues to stitches but these are rare problems. Small stitch abscesses can occur and stitches can come to the surface but these issues usually resolve without effecting the long term result.