Shortness of breath while exercising is sometimes a sign of asthma, which involves a narrowing and swelling of airways. Along with having difficulty catching your breath while exercising, you may cough. Summary. Shortness of breath is found among people with Herpes simplex, especially for people who are female, 60+ old, take medication Valtrex and have High blood pressure. Summary. Shortness of breath is found among people with Shingles, especially for people who are female, 60+ old, take medication Valtrex and have High blood pressure. The manufacturer's product labeling should always be consulted for a list of side effects most frequently appearing in patients during clinical studies. What Is Valtrex Exactly? Valtrex (or Valacyclovir) is a medicine used to treat infections caused by specific types of viruses. In kids, it is effective in the cases of chickenpox (caused by the virus called Varicella Zoster) and also the cold sores around the mouth (which are caused by the Herpes Simples virus). Along with its needed effects, valacyclovir (the active ingredient contained in Valtrex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. The manufacturer's product labeling should always be consulted for a list of side effects most frequently appearing in patients during clinical studies. Valtrex (valacyclovir) is an antiviral medication used to treat infections with: herpes zoster , herpes simplex genitalis (genital herpes), and herpes labialis. Valtrex is available in generic form. Valtrex is an antiviral drug that treats herpes. Learn more about the harmful effects it may have on the kidney, how it works, adverse reactions, and warnings. Learn more about the harmful effects it may have on the kidney, how it works, adverse reactions, and warnings. Valtrex is the brand name for valacyclovir, an antiviral drug used to treat infections caused by certain types of viruses. In adults, it's prescribed for shingles (herpes zoster), cold sores.