In univariate analyses larger tumour size (p=0.009), antihormonal therapy with aromatase inhibitors (p=0.005), larger breast volumes (p=0.004), smoking during EBRT (p=0.064) and absence of allergies (p=0.014) had an influence on skin toxicity after 3D-CRT (i.e. erythema G0 versus G1 versus G2). The gene discussed is CYP19A1; the disease is Allergy.