A rash with itchy blisters that has spread for a week.

As someone who has experienced this, I'm not lazy: the findings you described (blistered, red, itchy lesions spreading from the shoulders to the neck, chest, back, and face within a week) fit several possible causes, and a physical examination is needed for a definitive diagnosis.

Possible general causes (not certain):

• Allergic reaction or contact dermatitis (due to contact with new soap, detergent, clothing, perfume, cream, or food).
• Urticaria (itchy blister-like rash due to allergy, often spreading quickly).
• Viral rash or eczema flare-up. - Drug reaction (may be related to any recently started medication, supplement, or herbal product).
• Rarer causes: fungal/infectious skin lesions, parasitic infestations (e.g., scabies) — clinical examination required.

Short-term self-care suggestions:

• Stop starting and potentially triggering new products (new soaps, lotions, clothing detergents, cosmetics).
• Cold compresses, mild moisturizers, and oral antihistamines (e.g., loratadine, cetirizine) may help reduce itching. Consult a pharmacist/doctor if you have a chronic illness or are taking medication. - Avoid irritation: avoid hot showers, harsh soaps, and harsh scrubbing; wear loose cotton clothing. - Avoid makeup/creams if you have blisters and widespread lesions on your face; clean your face gently.

When to seek emergency/early assessment:

• Go to the emergency room immediately if you experience shortness of breath, chest pain, difficulty swallowing, rapid swelling of the lip/cheek/tongue, dizziness, or fainting (this may be a sign of anaphylaxis).
• Emergency assessment is necessary if the lesions are very painful, contain pus, have a fever, or are rapidly worsening. - Schedule an appointment with your family doctor/dermatologist if there is no improvement within a few days, if the lesions continue to spread, or if they affect your daily life.

Brief personal note: 24 years old, body mass index approximately borderline (slightly overweight); Inform your doctor about your general health and any current medications you are taking. Taking photos of any newly developed rashes to monitor changes and sharing them with your doctor is helpful.

If you wish, please include additional information such as any new medications, products, foods, or similar close contact history that started in the last two weeks, and any fever/respiratory symptoms; this will allow me to make more targeted recommendations. I am not a real doctor, and this is not a medical diagnosis.