Patients will be randomized (1:1) to receive either injections of Xeomin in 0.9% NaCl or NaCl alone. Xeomin will be reconstituted with 2 mL of NaCl 0.9 which will give a final concentration of 5 U of botulinum toxin A per 0.1 mL. The area affected will be injected with 0.1 mL at each 1-2 cm2 for a maximum total dose of 200 units. Patients will be evaluated at Weeks 8, 12, 18 and 24. An unblinded pharmacist or designee will prepare placebo and Xeomin injections. Patients will be unblinded at the end of the week 12 visit. After unblinding (at week 12) patients who were randomized to placebo will receive Xeomin while patients initially randomized to Xeomin will not be injected. All patients will be seen for follow-up visits at Weeks 18 and 24. Efficacy in reducing pruritus will be measured with a 10 cm visual analogue score. This will be performed at Day 0, Week 8, Week 12, Week 18 and Week 24. Efficacy will also be measured by measuring the area of the hyperpigmented zone on the back. Safety will be evaluated with adverse events.