Comedonal acne is a milder pattern made up mostly of blackheads and whiteheads, without much redness or visible inflammation. It generally responds well to topical treatments alone, without needing anything stronger. It's often where acne starts before, in some people, progressing to more inflamed forms.

Cutibacterium acnes is a type of bacteria that lives naturally on everyone's skin but can multiply inside clogged pores and contribute to inflammation. It's not the sole cause of acne, but it plays a meaningful role in inflamed lesions. That's part of why some acne treatments are designed to reduce bacterial activity.

A comedone is a small, clogged pore where oil and dead skin cells have built up — it's essentially where most acne starts. Depending on whether the pore stays open to the air or closes over, it becomes a blackhead or a whitehead. Understanding this early stage helps explain why prevention often focuses on keeping pores clear.

Chronic rhinosinusitis is long-term inflammation of the nose and sinuses lasting twelve weeks or more, and it's often the condition that nasal polyps grow out of. Congestion, facial pressure, and a reduced sense of smell are typical symptoms. Treating the underlying inflammation is usually key to managing the polyps themselves.

CASPAR criteria are a standardised checklist of features — joint symptoms, skin or nail changes, and certain test results — that doctors use to help confirm psoriatic arthritis. Having a shared set of criteria means diagnosis is more consistent from one clinic to another. It's mainly a tool used behind the scenes by specialists.

Chronic inducible urticaria refers to long-lasting hives that reliably show up in response to a specific physical trigger, such as cold, heat, pressure, or sunlight. What sets it apart from spontaneous urticaria is that the trigger can usually be pinned down. Once identified, avoidance strategies can be built around it.

Cold urticaria means the skin reacts with hives and swelling within minutes of touching something cold, whether that's cold air, water, or an object. Symptoms typically settle as the skin warms back up. Knowing about this trigger matters because a strong reaction after cold-water swimming can occasionally become serious.

Cholinergic urticaria produces a rash of small, itchy hives whenever the body temperature rises, whether from exercise, a hot shower, or stress. Overactive nerve signals to the sweat glands are thought to be behind the reaction. Once someone recognises heat as their trigger, adjusting activity or cooling down quickly can help limit flare-ups.

When hives keep coming back on most days for six weeks or more, and no obvious cause can be found, doctors call it chronic spontaneous urticaria. The immune system releases chemicals that trigger swelling and itching for reasons that are not always clear. It's a long-term condition, but one that usually responds well to ongoing treatment.

Cylindrical Bronchiectasis is a special type of imaging test. It means the mildest form where the airways are dilated but still straight. This scan gives doctors a very detailed picture of the lungs and airways. It helps confirm a diagnosis, shows how severe the condition is, and allows doctors to plan the most appropriate treatment.