Final answer:
Dermal thickening can occur due to calluses from friction, contact dermatitis from irritants, eczema, delayed-type hypersensitivity reactions, or inflammatory skin conditions like folliculitis and acne.
Step-by-step explanation:
The cause of dermal thickening can be attributed to several factors including age-related changes, skin conditions, and physical stimuli. For instance, repetitive pressure or friction on the skin can lead to callus formation, where the layer of the skin becomes thickened to protect the underlying structures. Conversely, as part of the natural aging process, the Integumentary System experiences a reduction in cell division, metabolic activity, and blood circulation, leading to a thinner epidermis. The dermis, however, may thicken in response to damage or inflammation, such as in the case of contact dermatitis which is often caused by exposure to irritants like latex, or eczema, an allergic response that manifests as a rash.
Dermal thickening can also be a reaction to chronic conditions of the skin, including delayed-type hypersensitivity reactions. These responses involve the immune system and result in skin inflammation that can lead to thickening of the dermis. Lastly, conditions like folliculitis and acne are examples of inflammatory responses to infections or clogged hair follicles, respectively, which can also result in localized thickening of the skin within affected areas.