The primary objective of the study is to assess the dosis of DL which is sufficient to inhibit cold urticaria symptoms.

A total of 30 patients (male and female) with ACU will be included in this study

Inclusion Criteria:

• Informed consent signed and dated
• Reliable method of contraception for both women of childbearing potential as well as man during the study and 3 months thereafter. A highly effective method of birth control is defined as those which result in a low failure rate (i.e. less than 1% per year) when used consistently and correctly such as implants, injectables, combined oral contraceptives, some IUDs, sexual abstinence or vasectomised partner
• Outpatients with ACU for more than 6 weeks. Urticaria symptoms must comprise wheal and itch.
• Age between 18 and 75 years

Exclusion Criteria:

• Subjects who are inmates of psychiatric wards, prisons, or other state institutions. Existing or planned placement in an institution after ruling according to § 40 passage 1 number 4 AMG (Arzneimittelgesetz).
• The presence of permanent severe diseases, especially those affecting the immune system, except urticaria and cold urticaria
• The presence of permanent gastrointestinal condition which may influence the oral therapy (chronic diarrhoea diseases, congenital malformations or surgical mutilations of gastrointestinal tract)
• History or presence of epilepsy, significant neurological disorders, cerebrovascular attacks or ischemia
• History or presence of myocardial infarction or cardiac arrhythmia which requires drug therapy
• Evidence of severe renal dysfunction
• Evidence of significant hepatic disease (liver enzymes twice the upper reference value)
• History of adverse reactions to DL
• Presence of active cancer which requires chemotherapy or radiation therapy
• Presence of alcohol abuse or drug addiction
• Intake of oral corticosteroids within 14 days prior to screening visit
• Use of depot corticosteroids or chronic systemic corticosteroids within 21 days prior to screening visit
• Use of systemic immunosupressants/immunomodulators like ciclosporine A, dapsone, methotrexate, mycophenolate, chloroquine, and comparable drugs within 28 days prior to screening visit.
• Pregnancy or breast-feeding