Nucleic acid can be done for a blister in the mouth and will have no effect on the test results. Nucleic acid testing is usually done by nasal or pharyngeal swabs to remove a specimen of upper respiratory secretions, which is then tested in the laboratory. In the case of a pharyngeal swab, the sampling location is the throat area, which usually does not touch the vesicles in the mouth. A nasal swab may also be used if the patient has a blister in the throat. A blister in the patient’s mouth may be caused by an infection such as a mouth ulcer or a break in the mucous membrane caused by eating too hot or too hard food, which in itself will not affect the results of the nucleic acid test. Nucleic acid can be done for blisters in the mouth, but care should still be taken not to touch the broken area when doing the nucleic acid, so as not to cause the wound to worsen.