Health and Safety
Visiting mountain towns and Lake Titicaca can bring on soroche (altitude sickness). Nonprescription remedies include mate de coca (coca tea) and pastillas de sorojchi (over-the-counter pills). As these latter contain only caffeine, aspirin, and an aspirin substitute, your own preferred headache remedy is just as good. Drink lots of bottled water and forego alcohol, coffee, and heavy meals at first. Be aware that prescription altitude medication is typically sulfa-based, a substance many people have allergies to. There is no substitute for proper acclimatization.
Colca Canyon is generally safe, as are Arequipa and Puno. Nevertheless, don't walk alone at night, know where your money is, and educate yourself on the good and bad parts of town. Police presence has increased in Arequipa. Use only recommended taxi companies, or have someone call one for you. But walking around the plaza, even at night, is safe in Arequipa. Hiking El Misti alone is not recommended. Puno is generally safe in the tourist areas, but at night the port and the hills should be avoided.