Misc Derm: Sun + Bug Bites

Ultraviolet Radiation (UVR)

• Consists of light beyond the visible spectrum
• Divided by frequency into UVA, UVB and UVC

UVA

• Minimally absorbed by the ozone layer
• Deeply penetrates skin
• Causes skin cancer
• Most associated with aging and pigmentation

UVB

• 90% absorbed by the ozone layer
• Minimally penetrates skin
• Causes skin cancer
• Most associated with burns

UVC

• 100% absorbed by the ozone layer
• Most damaging

UV Exposure

• Exposure impacted by time of day/year, latitude, altitude, humidity, clouds/haze and ground reflection
• The UV index is an international standard to measure the strength of the sun's UV rays
• High UV index numbers indicate a greater need for sun protection
• Factors include latitude, cloud cover, humidity and precipitation

Acute Sun-Induced Skin Damage: Sunburn

• Represents an inflammatory response to skin cell damage caused by UV radiation
• Onset is typically 2-6 hours, and it resolves in 72-120 hours
• Local symptoms: erythema, edema, pain, pruritus and blistering
• Systemic symptoms: N/V, fever, chills, weakness and headache

Acute Sun-Induced Skin Damage: Phototoxic Reaction

• A drug or metabolite in the patient's exposed skin absorbs UV radiation, leading to chemical reactions and skin damage
• Onset within minutes to hours
• Self-limiting with discontinuation of medication
• Appears similar to an exaggerated sunburn in exposed areas

Acute Sun-Induced Skin Damage: Polymorphic Light Eruption

• A photosensitive disorder with genetic and environmental factors (UV)
• Characterized by intermittent groups of itchy pink or red papules
• Onset within a few hours
• Resolves within a couple of weeks, returns with UV exposure

Acute Sun-Induced Skin Damage: Solar Urticaria

• A rare, chronic condition
• The mechanism is not well understood, but may involve an antibody-mediated immune reaction
• Manifests as hives
• Onset minutes post UV exposure
• Resolves minutes to hours

Chronic Sun-Induced Skin Damage: Squamous Cell Carcinoma

• The 2nd most common type of skin cancer
• Occurs when UVR triggers changes in squamous cells
• Represents chronic, cumulative lifetime exposure
• Appears as scaling or a crusty lesion that may be raised and wart-like
• Lesions may bleed or erode over time

Chronic Sun-Induced Skin Damage: Basal Cell Carcinoma

• The most common type of skin cancer
• Occurs when UVR triggers changes in basal cells
• Related to episodic sun exposure during childhood, especially on the face
• Appears as small, dome-shaped lesions that slowly expand and develop a central ulceration

Chronic Sun-Induced Skin Damage: Melanoma

• The most dangerous type of skin disease
• A disease in which malignant (cancer) cells form in melanocytes
• Related to intense and intermittent sun exposure in childhood
• Appears as a flat brown or black spot (commonly in a mole or dark spot) with irregular edges that may grow larger

Melanoma Assessment: ABCDE

• A: Asymmetry, one half is unlike the other half
• B: Border, irregular, scalloped or poorly defined
• C: Color, varied from one area to another, shades of tan, brown, black; sometimes white, red or blue
• D: Diameter, melanomas are usually greater than 6mm when diagnosed
• E: Evolving, a mole or skin lesion that looks different from the rest or is changing in size, shape or color

Chronic Sun-Induced Skin Damage: Photoaging

• Includes freckles, solar lentigo (age/liver spots)
• Actinic keratoses are sun induced lesions that can turn into carcinoma
• More common in light skin, men, aged >50
• Appearance: firm, scaling, erythema

Sun Protection: Seek Shade

• Especially needed between 10 a.m. to 4 p.m. and for children < 6 months old

Sun Protection: Protective Clothing

• Fabrics with UPF >25 are best
• Long-sleeved shirts and pants, dark color with a tightly woven fabric
• Wide brim hats and sunglasses.

Sun Protection: Sunscreen

• In Canada, sunscreen products have a Drug Identification Number (DIN)
• Sunscreens are barriers applied to the skin
• Either absorb or reflect the sun's UV rays
• Formulations available include creams, lotions, sprays, gels and sticks

Sunscreen: Physical

• Offer highly effective UVA and UVB photoprotection
• Faster onset
• Possible white cast, thicker, more difficult to apply
• Often better tolerated and may cause heat rash or folliculitis

Sunscreen: Chemical

• Some absorb UVA or UVB, some do both
• Need time to bind to skin
• Absorbed and not visible
• Can be irritating, can also cause allergic contact dermatitis

Special Populations: Infants/Children

• Nonpharmacologic measures are the 1st choice
• Sunscreen is not recommended for infants < 6 months of age
• Consider physical blocks on small surfaces only if needed

Special Populations: Pregnancy & Lactation

• Nonpharmacologic measures are the 1st choice
• Chemical and physical sunscreens are both considered safe as an additional option

Patient Education

• Use sunscreen in addition to nonpharmacologic recommendations
• Apply liberally and reapply regularly every 2 hours, before sun exposure and after swimming or sweating
• Do not use sunscreen to extend time spent in the sun

Sunscreen: Patient Application

• A teaspoon is needed for each arm, leg, front, back and face/neck area (total of 7 teaspoons.
• Choose sunscreens with:
  • Broad-spectrum (UVB and UVA coverage)
  • SPF of >30 (only effective if adequately applied)
  • Low potential for irritation
  • Minimal perfumes
  • Non-comedogenic
  • Water Resistant (provides SPF benefits after swimming)
  • Not expired (may become less effective and more irritating)
• Homemade sunscreen recipes are dangerous and do not work

Insect Bites vs Stings: Learning Objectives

• Differentiate between insect bites and stings
• Recommend preventative measures and treatments for local reactions
• Recognize signs/symptoms of systemic reactions
• Recommend pharmacologic treatment for systemic reactions
• Identify when to refer patients to other healthcare providers

Insect Bites and Stings: Etiology and Pathophysiology

• Bites are caused by spiders, ticks, centipedes, mosquitos, ants, black flies, and horseflies
• Stings are caused by bees, wasps, fire ants and scorpions
• Injury is a localized, self-limiting skin reaction involving raised papules and urticaria
• Possible sequelae: allergic reactions, secondary infections, transmission of disease and, rarely, death

Mosquito Bites

• Red, itchy papules appearing within hours
• Some may have large welts that develop and last several days
• Anaphylaxis is rare
• Transmit diseases like malaria, zika, West Nile and other viruses

Bed Bug Bites

• Red, itchy lesions
• Typically found in clusters of 3–5 in a line, curve or zigzag pattern on arms and legs
• Anaphylaxis is rare
• Classified as not definitively vector

Tick Bites

• Present as a red papule
• May cause swelling, blistering, bruising, itching or secondary skin infections
• Anaphylaxis is uncommon
• Known vector of Lyme Disease, rocky mountain spotted fever, and others

Spider Bites

• Cause localized stinging, itching and inflammation
• Black widow or brown recluse bites can cause severe symptoms such as tachycardia, chest pain, respiratory depression, infection and necrosis
• Anaphylaxis is rare
• Classified as non-vectors

Bee/Wasp/Hornet Stings

• Associated with pain, redness, and swelling within 4-48 hours
• Multiple stings can lead to systemic reactions (headache, fever, N/V)
• Anaphylaxis is possible
• Classified as non-vectors

Insect Bites and Stings: Prevention

• Wear clothing that covers skin with tight ankles/wrists, tuck socks into gloves and choose light colors
• Mosquito netting and Window Screens and Air Conditioning
• Insect Repellents

Repellents: DEET

• The vapor has an offensive smell/taste to insects
• Effective against mosquitoes, black flies, ticks, chiggers and fleas
• Concentrations vary from 5% to 20-30+%
• Concentrations >10% is not demonstrated to be effective against ticks
• Dosing: up to TID, varies based on age, patients 6 months to 12 years of age should avoid concentrations > 5-10%
• Absorbed through intact skin, and systemic effects correlate to the amount absorbed/ingested
  • Local effects include irritation to mucous membranes, eyes and wounds, and contact dermatitis.
  • If ingested, results in N/V and oral irritation
  • Systemic effects include seizures, tremor, hypotension, angioedema or death

Insect Repellents: Icaridin/Picaridin

• Affects the insects ability to detect the host by concealing attractants
• Effective against mosquitoes, ticks and black flies
• Concentrations include 10% and 20%
• Dosing: 2-4 times daily, varies based on strength.
• Low toxicity, non-irritating (compared to DEET), avoid contact with eyes and mouth
• No allergic reactions reported
• All strengths considered safe ≥ 6 months*

Natural/Biopesticides

• Lemon Eucalyptus Oil/PMD: for ages ≥ 3y, duration 2-5h
  • Mosquitoes and black flies only, no protection against ticks
• 2% Soybean oil: safe for ages 2+, lasts 3.5-8h.
  • Effective against mosquitos and black flies and is a similar to DEET 10%
• Citronella: safe for ages 2+, short duration is 30min - 2h
• Tested only against mosquitoes

Insect Repellents: Special Populations

• Infants < 6 months: In Canada, the use of insect repellent products is not recommended
• Outside of Canada, experts suggest either Icaridin or DEET, along with nonpharmacologic protective measures
• Pregnant or Breastfeeding women
  • ≤30% DEET or ≤20% Icaridin, used to a maximum of BID, also 2% soybean oil can be used without restriction

Patient Assessment for Bites

• Determine if there is significant pain and swelling extending beyond the initial lesion.
• Determine if Reaction larger than 10 cm in diameter or persisting longer than several days.
• Refer patient for further assessment and/or treatment when the answers are yes

Patient Assessment for Stings

• Determine if the patient is having a Systemic reaction/ anaphylaxis (within 30 min)
• Determine if they are having allergy symptoms, a sting to the tongue or mouth, a history of reaction to previous stings, or if they are under the age of two
• For negative answers treat locally, for positive, refer patient for further assessment and/or treatment

Insect Bites and Stings: Treatment

• Nonpharmacologic: Cleanse with warm soapy water to prevent 2° infection, ice or cool compress, home remedies
• Refer to allergist/immunologist for skin testing
• Pharmacologic Includes oral and topical options

Treatment

• Oral Antihistamines and analgesic
• Topical corticosteroid or antihistamine.
• Astringents and ammonia/baking soda for pain relieve/ itch

Serious Sequelae: Secondary Infection

• Lyme disease, Anaplasmosis, Babesiosis, Powassan virus disease from ticks
• Zila, malaria and dengue from masquitos
• Bacteria can use Injury from bite or sting to enter the body

Serious Sequelae: Anaphylaxis

• Is a severe, life-threatening, hypersensitivity reaction.
• Rapidly developing problems involving the airways, breathing, circulation and the skin/mucousa. A call to 911 is important.