Stress influences the skin and hair through hormones and the immune system. It can trigger flares of inflammatory skin conditions such as eczema, psoriasis and rosacea, worsen acne, and in some people bring on outbreaks of hives. Stress can also drive habits like scratching or skin-picking that aggravate problems.
For hair, a significant physical or emotional stressor can push many follicles into the resting phase, leading to noticeable shedding (telogen effluvium) a couple of months later. This is usually temporary, with regrowth once the stress resolves. Severe stress is also associated with patchy hair loss in alopecia areata in susceptible people.
Managing stress through sleep, exercise, relaxation techniques and support can help, alongside treating the skin or scalp condition itself. See a doctor if symptoms are persistent, distressing or not improving, or if hair loss is patchy or ongoing, since other causes should be excluded and effective treatments may be available. This is general information, not a diagnosis.