Yes, it is safe. The chances of transmission when no visable sores are present is extremely slim. If the person is on anti-viral therapy (valtrex), the chances are even less. You may want to present this question to the STD forum, as Dr. Handsfield would be able to give you more insight on this.
'Chlamydia, human papillomavirus (HPV), gonorrhea, herpes, hepatitis (multiple strains), and other sexually transmitted diseases (STDs)—including HIV—can be transmitted through oral sex.'
'If the receiving partner has wounds or open sores on their genitals, or if the giving partner has wounds or open sores on or in their mouth, or bleeding gums, this poses an increased risk of STD transmission.'
You could read more about this at the following link -
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