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The causes of your symptoms cannot be exactly diagnosed just by the description provided by you.
It could be due to a condition called impetigo (infection due to staphylococcus) which can cause itching and bumps on the scalp. Skin conditions like Seborrheic dermatitis, Psoriasis, Eczema also can be a possible cause of your symptoms.
If the bumps on your scalp persist for more than one week or get worse, medical evaluation may be needed to determine the need for specific treatment. Hence you should consult with your doctor or a dermatologist for proper advice.