I'm sorry to hear you're experiencing pimples on your back and shoulders. This condition is commonly known as back acne or "bacne." It can be caused by factors such as excess oil production, clogged pores, sweat, friction from clothing, or bacterial growth.

Here are some helpful tips to manage and reduce pimples in these areas:

• Keep the skin clean: Gently wash your back and shoulders daily with a mild cleanser to remove sweat and excess oil.
• Avoid harsh scrubbing: This can irritate the skin and worsen acne.
• Wear breathable clothing: Choose loose-fitting clothes made of natural fibers to reduce sweat and friction.
• Avoid heavy lotions or oils: These can clog pores further.
• Shower after sweating: Especially after exercise, to prevent pore blockage.
• Consider over-the-counter treatments: Products containing benzoyl peroxide or salicylic acid may help reduce acne.

If the pimples are persistent, painful, or worsening, it is important to consult a dermatologist (skin specialist). They can evaluate your condition and may recommend prescription treatments such as topical or oral medications.

Please seek professional advice to get a tailored treatment plan for your skin condition.To narrow down potential causes, we will need some more information.Please tell me your age and gender.