Cholinergic urticaria and unable to sweat

Hi Jacob, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the cholinergic urticaria and the inability to sweat.
Anhidrosis is the term used for inability to sweat. Anhidrosis may be caused by underactivity of the sympathetic nervous system.
When you don't perspire, your body can't cool itself, which can lead to overheating and sometimes to heatstroke — a potentially fatal condition. Anhidrosis can develop on its own or as one of several signs and symptoms of another disorder, such as diabetes, neuropathy or psoriasis. Many illnesses can damage your autonomic nerves, including diabetes, alcoholism, Parkinson's disease, amyloidosis — a serious disease that occurs when substances called amyloid proteins build up in your organs — Sjogren's syndrome, which causes dry eyes and mouth, and small cell lung cancer. Anhidrosis is the hallmark of Ross syndrome, a peripheral nerve disorder.
Rare metabolic disorders, such as Fabry disease, also are associated with anhidrosis.
Anhidrosis can occur with a number of skin disorders, including psoriasis; exfoliative dermatitis, which is marked by severe skin scaling; heat rash; scleroderma, which causes hard, tight skin; and ichthyosis — extremely dry, scaly skin.
Your doctor is likely to suspect anhidrosis based on your signs and symptoms, a thorough medical history and physical exam, but you may need certain tests to confirm the diagnosis. These include:
1. Reflex test. In a test called a quantitative sudomotor axon reflex test (QSART), a small, painless electrical current passes through four electrodes placed on your forearm, foot and leg to activate the nerves that supply your sweat glands. The volume of sweat produced by this stimulation is then measured. You may feel a mild tingling or slight burning sensation during the test.
2. Silastic sweat imprint. This test measures the distribution of perspiration by taking an imprint of drops of sweat in a rubbery material (Silastic).
3. Thermoregulatory sweat test. During this test, you're coated with a powder that changes color when you sweat. You then enter a chamber that causes your body temperature to increase to a level that makes most people perspire. Digital photos document the results.
Sometimes the cause of anhidrosis or hypohidrosis is never found.
You can start with an appointment with your GP but you may need an appointment with a dermatologist to find the cause of the condition.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.