Incorporate a hygiene class into your everyday curriculum. Address topics such as the proper way to brush your teeth, body washing, the importance of wearing clean clothes and not picking your nose in public. Every student can benefit from a hygiene class, but this also makes the offender not feel singled out. This is the easiest way to address a hygiene problem without embarrassing anyone.
Contact local stores and companies requesting free samples of hygiene products. Shampoos, toothpaste, body soap and conditioners all come in small, sample sizes. Give these to all students, once again, not singling out the offender. Explain why each product should be used, doing your best not to sound pedantic.
Have the student with the poor hygiene habits meet you before or after class. Sit him down and explain the importance of proper hygiene. Make the student aware of the social ramifications, as well as the medical complications that can come from poor hygiene. The student may be unaware that he is offending others, or may not know how to rectify the problem. Intersperse the conversations with positive affirmations about the student.
Send a note home to the student's parents if you don't see an improvement is not seen.