The red spots on your limbs appear consistent with an acute irritant or allergic contact dermatitis, or possibly early vasculitic or viral exanthem depending on systemic symptoms and distribution.
Next Steps
Avoid any new topical products or allergens. An antihistamine may help with itching, but a more precise diagnosis and treatment (like topical steroids) require a proper online consult with close-up images and history.
Health Tips
Keep the skin moisturized with fragrance-free emollients, avoid scratching, and monitor for new lesions or systemic symptoms like fever or joint pain.