Lecture 12

A skin infection caused by hookworms that live in dogs and cats. It commonly affects the feet and presents as a red, itchy, winding line.

The hookworms responsible for CLM cannot penetrate the deeper layers of the skin, so they remain in the epidermis.

CLM usually resolves on its own when the worm dies. It can also be treated with anti-helminthic medications, such as ivermectin or albendazole.

Insect bites and stings cause immediate, delayed allergic, or delayed toxic reactions.

Immediate reactions occur immediately after the bite and are caused by substances in the insect's venom.

Delayed allergic reactions occur hours to days after the bite and are caused by an allergy to substances in the insect's saliva.

Delayed toxic reactions develop after the bite and can be localized or systemic.

Spider bites are a classic example of delayed toxic reactions.

Reactions caused by toxins injected by spiders, such as brown recluse bites (ulcers) and black widow bites (neurological symptoms).

Reactions that occur shortly after a sting or bite, typically caused by insects like fire ants, bees, and wasps.

The most effective insect repellent, commonly used to prevent bites from insects that feed on human blood.

A skin rash caused by contact with tiny larvae of certain types of marine worms in saltwater.

A skin rash caused by contact with parasites (cercariae) in freshwater, typically lakes and ponds.

A severe allergic reaction, often triggered by bee or wasp stings, requiring immediate medical attention.

A device that allows individuals to self-administer epinephrine, which is crucial for treating anaphylaxis.

Medications that help relieve symptoms of allergic reactions, including itching, rash, and inflammation.

A skin rash that occurs after swimming in contaminated water, typically hot tubs or pools, due to exposure to the bacteria Pseudomonas aeruginosa.

The larvae of the schistosoma parasite that causes Swimmer's Itch.

A type of jellyfish larvae that cause Seabather's Eruption, a skin rash similar to Swimmer's Itch but caused by a different organism.

The tiny stinging cells of jellyfish and anemones that cause Seabather's Eruption.

The main bacterial cause of Hot Tub Folliculitis.

A skin reaction to UV radiation from the sun.

A condition often caused by exposure to sunlight, most common in fair-skinned individuals.

A suntan from tanning beds won't protect you from sunburn as well as a natural tan because tanning beds primarily emit UVA rays, which increase melanin production (tanning) but not epidermal thickening, which is key for true sun protection.

Phytophotodermatitis is a skin condition that occurs after exposure to certain plants (like limes) combined with sunlight. It presents as brown discoloration on the skin, often appearing 1-2 weeks later and lasting up to 2 years.

The characteristic patterns of phytophotodermatitis are often linear streaks (from a drop of lime running down the chest), rings or lines on the abdomen (from a glass resting on the area), or irregular spots on the hand (from a splash).

Phytophotodermatitis is caused by furocoumarins, chemicals found in limes and some vegetables. When these chemicals are activated by sunlight, they damage DNA.

There is no specific treatment for phytophotodermatitis. The pigmentation usually fades over time, taking up to 2 years.

Poison ivy allergy is very common, affecting 50-70% of people. It's more prevalent during summer and fall.

Sunburn is caused by damage to the epidermis from UV radiation, specifically UVB, which directly interacts with keratinocyte DNA, leading to inflammation and also generates free radicals that cause further inflammation.

Sunburns usually lead to peeling of the affected skin as it heals, and in severe cases, permanent dark spots (lentigines) can appear.

Sunburns have a gradual onset, typically becoming noticeable 4-24 hours after exposure. The severity dictates the healing time, ranging from 1 day for mild burns to weeks for severe burns.

A suntan offers protection in two ways: melanin production absorbs UV radiation, and epidermal thickening reduces UV penetration.

UVA radiation primarily stimulates melanin production, while UVB radiation mainly causes epidermal thickening.

UVB, known as "burning rays", is about 1/20th the intensity of UVA, known as "tanning rays", reaching the Earth's surface.

The amount of UVB reaching the Earth's surface fluctuates significantly throughout the day and year, unlike UVA which remains fairly constant.

Preventing sunburn is crucial and involves using sunscreen, protective clothing, and limiting sun exposure. When a sunburn occurs, applying topical steroids, taking anti-inflammatory medications, and keeping the skin moisturized can help alleviate symptoms.

Poison ivy and oak cause an allergic reaction on second exposure. The allergic substance is called urushiol.

It's an oily substance found in the leaves, stems, and roots of poison ivy and oak.

The rash of poison ivy/oak is called an erythematous, edematous eruption with streaks of vesicles.

It usually takes 6 hours to 6 days to appear after exposure if you've been sensitized. But, the first exposure can cause both sensitization and the rash.

Washing within 30 minutes of exposure can help prevent the reaction. But, it's less effective after 30 minutes.

On first exposure, urushiol is taken up by immune cells, presented to lymphocytes, and memory T-cells are created.

On re-exposure, memory T-cells recognize the urushiol and trigger an immune response, leading to the allergic reaction.

Both poison ivy and oak contain urushiol, which is a potent sensitizer that triggers allergic contact dermatitis.