Hives are a kind of skin rash that are red, raised, and are itchy or sting; they affect an estimated 15 to 20% of population. A unique characteristic of hives is - they can rapidly change in shape or size. And yes, they can be extremely annoying, although rarely that serious.
So, can stress cause hives? Short answer - YES!
But, the most common cause of hives is? Allergy. It can be contact, or food allergy. But hives with allergen causes tend to disappear in few days, or at the most in few weeks.
Other causes include immune deficiency problems, viral infections, or yes, stress - generally of prolonged nature. There is research that links stressful events in one's life - like death in the family, or loss of job - to the occurrence of hives. Hives caused by these reasons tend to stay longer than few weeks, and may need your doctor's attention.
If hives are accompanied by fever, it is a good idea to get them checked by your doctor as soon as possible.
Otherwise, treatment typically involves avoiding contact with allergens (if that has been established as the cause), over the counter antihistamines, or prescribed cortisone drugs. Simple techniques like avoiding hot showers, and not wearing tight clothing that can further irritate your skin, will help as well.
For more serious stress concerns, it may also be a good idea to seek the help of a professional therapist.