• Males and females, \>/= 18 years of age.

• Diagnosis of cold induced urticaria or symptomatic dermographism \>/= 3 months.

• Diagnosis of cold induced urticaria or symptomatic dermographism despite the use of a stable regimen of second generation non-sedating H1-antihistamine as defined by:

‣ The presence of hives for \>/= 6 weeks at any time prior to Visit 1 despite the use of H1-antihistamines.

⁃ Must be on a stable regimen of second generation non-sedating H1-antihistamine for \>/= 4 weeks prior to study treatment.

⁃ Cold induced urticaria: A Critical Threshold Temperature (CTT) of ≥ 10 °C and \< 37 °C using the TempTest® and a numerical rating scale score of ≥ 3 for itch after the provocation test.

⁃ Symptomatic dermographism: A Critical Friction Threshold (CFT) of ≥ 3 using the FricTest® and a numerical rating scale score of ≥ 3 for itch after the provocation test.

• Cold induced urticaria: Positive ice-cube test resulting in hives at the provocation site during Screening

• Normal blood counts and liver function tests.

• Both males and females of child-bearing potential must agree to use highly effective contraceptives during the study and for 150 days after treatment.

• Willing and able to complete a daily symptom electronic diary and comply with study visits.

• Participants with and without prior biologic experience are eligible.