Hello, * As per my clinical experience, the welts on upper spine with minor itch and soreness indicate allergic reaction to the massage pad used. * The release of histamine cause tiny skin eruptions with red flaring, erythema and blotches with itch sensation. * Usually, mild case resolve after some minutes on its own, but severe cases may manifest as generalised itch, low blood pressure or other sequences of systemic anaphylaxis. * It is best recommended that - avoid future use of this type of massage pad - local application of ice over the affected part - intake of anti histamine as diphenhydramine or cetrizine for itch relief - plenty of liquids to prevent lowering of blood pressure * Should consult your primary care for further guidelines if needed. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr. Bhagyesh V. Patel