This cross reaction can cause problems in interpreting results from CFTs and other tests. Herpes labialis (cold sore) is a recurrence of oral HSV. Large doses of steroids in the management of asthma or rheumatoid arthritis have similar effects. A. Cold sores, also called fever blisters, can be painful and look yucky. One oral surgeon wrote to say his patients do well on a preventive regimen of one 500 mg tablet of l-lysine daily. Since on valtrex, one year now, I have had three minor outbreaks, I think mainly due to missing a dose. Question: I used to get cold sores about two to three times a year. They’re packed full of viral particles of the herpes variety. You could spread it to other parts of your body by direct contact, and if you kissed someone at that time or engaged in oral sex, you’d surely pass on the cold sore virus. Steroids can trigger psychiatric reactions. What is the varicella-zoster virus and how does it cause shingles? People with compromised immune systems, a natural consequence of aging or from use of immunosuppressive medications such as prednisone, are at increased risk of developing shingles. Most people who get shingles have it only once, but it is possible for the outbreak to appear again.