ailanthus, hahnemann directed in cases of skin complaints against applying a remedy to affected skin in order to obviate the possibility of suppressing the skin disease by direct contact with the remedy.
by the same token, injecting remedies at sites of pain seems to me to be contraindicated.
a correct remedy will work on the whole energy of the patient, setting to right the totality which then has an effect on symptoms. by applying the remedy to an affected site one risks a local effect only = suppression.