- The skin participates directly in thermal, electrolyte, hormonal, metabolic, and immune regulation.
- Percutaneous absorption depends on the xenobiotic's hydrophobicity, which affects its ability to partition into epidermal lipid, and rate of diffusion through this barrier.
- The cells of the epidermis and pilosebaceous units express biotransformation enzymes.
- Irritant dermatitis is a nonimmune-related response caused by the direct action of an agent on the skin.
- Allergic contact dermatitis represents a delayed (type IV) hypersensitivity reaction, whereby minute quantities of material elicit overt reactions.
The skin protects the body against external insults in order to maintain internal homeostasis. It participates directly in thermal, electrolyte, hormonal, metabolic, and immune regulation. Rather than merely repelling noxious physical agents, the skin may react to them with various defensive mechanisms that serve to prevent internal or widespread cutaneous damage. If an insult is severe or intense enough to overwhelm the protective function of the skin, acute or chronic injury becomes readily manifest. The specific presentation depends on a variety of intrinsic and extrinsic factors including body site, duration of exposure, and other environmental conditions (Table 19–1).
Table 19–1 Factors influencing cutaneous responses. |Favorite Table|Download (.pdf)
Table 19–1 Factors influencing cutaneous responses.
Thick stratum corneum—good physical barrier
Common site of contact with chemicals
Occlusion with protective clothing
Intertriginous areas (axillae, groin, neck, finger webs, umbilicus, genitalia)
Moist, occluded areas
Enhanced percutaneous absorption
Surface lipid interacts with hydrophobic substances
Chemicals frequently transferred from hands
Poor barrier function—thin epidermis
Sensitive to irritants
Hair follicles susceptible to metabolic damage
Predisposing cutaneous illnesses—atopic dermatitis
Increased sensitivity to irritants
Impaired barrier function
Impaired barrier function
Predisposition to skin disorders
Variation in sensitivity to irritants
Susceptibility to contact sensitization
Vasodilation—improved percutaneous absorption
Variation in relative humidity
Chapping and wind-related skin changes
The skin consists of two major components: the outer epidermis and the underlying dermis, which are separated by a basement membrane (Figure 19–1). The junction ordinarily is not flat but has an undulating appearance (rete ridges). In addition, epidermal appendages (hair follicles, sebaceous glands, and eccrine glands) span the epidermis and are embedded in the dermis. In thickness, the dermis makes up approximately 90 percent of the skin and has largely a supportive function. Separating the dermis from underlying tissues is a layer of adipocytes, whose accumulation of fat has a cushioning action. The blood supply to the epidermis originates in the capillaries located in the rete ridges at the dermal–epidermal junction. Capillaries also supply the bulbs of the hair follicles and the secretory cells of the eccrine (sweat) glands. The ducts from these glands carry a dilute salt solution to the surface of the skin, where its evaporation provides cooling.
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessPharmacy Full Site: One-Year Subscription
Connect to the full suite of AccessPharmacy content and resources including 30+ textbooks such as Pharmacotherapy: A Pathophysiologic Approach and Goodman & Gilman's The Pharmacological Basis of Therapeutics, high-quality videos, images, and animations, interactive board review, drug and herb/supplements databases, and more.
Pay Per View: Timed Access to all of AccessPharmacy
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.