What is a strange rash that seems to start with bruise and started on your thigh now back both legs arms itchy all day but extremely worse night?

There are several potential causes for this type of rash, but without a physical examination, it is difficult to determine the exact cause. Some possibilities include:

1. Vasculitis: This refers to inflammation of the blood vessels. It can cause a range of skin problems, including rashes, bruises, and itching.

2. Allergic reaction: An allergic reaction to a medication, food, or environmental allergen can cause a rash that is itchy and worse at night.

3. Insect bites: Insect bites can cause itchy, red, and raised areas on the skin. If you have been bitten by multiple insects, the bites may appear in clusters and resemble a rash.

4. Eczema: Eczema is a chronic skin condition that causes dry, itchy, and inflamed skin. It can affect any part of the body, including the thighs, legs, arms, and back.

5. Psoriasis: Psoriasis is a chronic skin condition that causes red, scaly patches of skin. It can affect any part of the body, including the thighs, legs, arms, and back.

6. Contact dermatitis: Contact dermatitis is a skin rash caused by direct contact with an allergen or irritant. It can cause itching, redness, and swelling.

7. Scabies: Scabies is a contagious skin condition caused by tiny mites that burrow under the skin. It causes intense itching, especially at night.

If the rash is severe, widespread, or accompanied by other symptoms such as fever, headache, or difficulty breathing, it is important to see a doctor as soon as possible. They will be able to diagnose the cause of the rash and recommend appropriate treatment.