Skin Reactions to Cold and Heat Exposure

Reaction to Cold

• Exposure to extreme cold can result in skin reactions in anyone.
• Persistent sores or growing lumps within a cold-induced rash may require a skin biopsy to rule out skin cancer.
• Abnormally pigmented areas of skin due to cold exposure can persist for years.
• Treatment options for cold-induced skin pigment changes include topical tretinoin or laser therapy.

Erythema ab igne (EAI)

• EAI is a skin condition caused by repeated exposure to heat, typically from sources like heating pads or fireplaces.
• It presents as a reddish-brown, reticular pattern on the skin, often resembling a "fire mark".

Miliaria (Sweat Rash)

• Miliaria occurs when sweat glands become blocked, leading to trapped sweat.
• This blockage can be caused by factors like heat, humidity, and tight clothing.
• Miliaria often results in a rash with small, itchy bumps.
• Immediate darkening of the skin pigment can occur.

Photoallergic Reaction

• Photoallergic reaction is an immune reaction that occurs after exposure to ultraviolet (UV) light.
• Unlike a sunburn, it takes several days to develop and involves delayed hypersensitivity.

Phototoxic Reaction

• Phototoxic reactions are caused by a direct chemical reaction between a substance and UV light, leading to skin damage.
• These reactions often occur quickly, within minutes to hours of UV exposure.

UV Radiation

• UVB radiation (290–320 nm) is responsible for:
  • Sunburn
  • Phototoxic reaction
  • Delayed pigment darkening
  • Premalignant and malignant skin conditions
• UVC radiation (200–290 nm) is more damaging and associated with:
  • Actinic keratosis
  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Malignant melanoma

Skin Pigmentation

• Immediate pigment darkening is a temporary darkening of the skin following UV exposure.
• This pigmentation change typically appears within minutes and lasts for a few hours.

Frost Bite

• Frostbite is an abnormal reaction to cold exposure that affects a small, susceptible portion of the population.
• Genetic predisposition likely plays a role.
• Examples of abnormal cold reactions include chilblains, cryoglobulinemia, and others.

### Chilblains (Perniosis)

• An abnormal vascular response to cold exposure, resulting in painful, inflammatory lesions.
• Commonly affects older children and young adults.
• Occur in the middle of the epidermis.

Miliaria Profunda

• Blockage at or below the dermo-epidermal junction following repeated episodes of miliaria rubra.
• Asymptomatic, flesh-colored, firm papules (2-3 mm in size).

Treatment for Chilblains

• Avoid hot exposure.

Senile Skin Changes

• Solar elastosis.
• Senile comedones.
• Telangiectasia.
• Poikiloderma of Civatte.

Premalignant and Malignant Skin Conditions

• Primarily caused by UVB radiation.

Phototoxic Reactions

• Resemble an exaggerated sunburn or blisters.
• Occur in sun-exposed skin.
• Not immunologically mediated.
• High incidence (affecting all people).
• Require large amounts of the agent.
• Onset occurs within minutes to hours.
• Only a single exposure is needed.

Photoallergic Reactions

• Dermatitis-like reaction.
• Occur in sun-exposed skin, potentially spreading to unexposed areas.
• Immunologically mediated (Type IV hypersensitivity).
• Low incidence (predisposed individuals).
• Require small amounts of the agent.
• Onset takes 24-72 hours.
• Multiple exposures are needed.

Photosensitizing Agents

• Tetracyclines
• Phenothiazines
• Amiodarone
• Nalidixic acid

Phytophotodermatitis

• Photosensitivity responses resulting from contact with plants or their products on sun-exposed areas.

Abnormal Reactions to Sun Exposure (Photodermatoses)

• Photodermatoses are abnormal reactions to sun exposure.
• Metabolic diseases can cause photodermatoses, including:
  • Porphyria
  • Xeroderma pigmentosum
  • Pellagra
• Drug-induced photodermatoses can occur due to both topical and systemic medications.
• Diseases aggravated by sunlight include:
  • Actinic lichen planus
  • Erythema multiforme
  • Lupus erythematosus
• Idiopathic photodermatoses have unknown causes, and include a variety of conditions:
  • Polymorphic light eruption
  • Solar urticaria
  • Chronic actinic dermatitis
  • Hydroa aestivale (summer prurigo of Hutchinson)
  • Hydroa vacciniform
  • Juvenile spring eruption
  • Actinic reticuloid

Perniosis (Chilblains)

• Inflammatory response of the skin, triggered by cold exposure
• Symptoms include redness, itching, and swelling
• Treatment involves avoiding cold exposure
• Topical treatments include corticosteroids and capsaicin cream
• Oral medications like nifedipine are used for severe cases to improve blood circulation
• Moisturizers prevent dry skin

Erythema Ab Igne

• Skin condition caused by prolonged exposure to heat
• Leads to a red, mottled appearance on the skin
• Avoiding heat sources is crucial
• Topical corticosteroids are used to reduce inflammation
• Retinoids can be applied to improve skin texture
• Avoiding future thermal injuries is recommended

Milaria (Heat Rash)

• Blocked sweat glands cause sweat retention, leading to the condition
• Staying in a cool environment and removing excess clothing are important
• Calamine lotion helps soothe irritation, while antihistamines relieve itching
• Wearing breathable fabrics and hydration help prevent heat rash

Phototoxic Reactions

• Occur after exposure to UV light when using certain medications or substances
• Remove the offending agent immediately if possible
• Cool compresses and soothing lotions, like aloe vera, can be applied
• Corticosteroids help reduce inflammation
• Sun protection measures like broad-spectrum sunscreen and protective clothing should be implemented

Photoallergic Reactions

• An immune-mediated reaction triggered by UV light after applying photosensitizing agents
• Discontinue using the offending agent
• Topical corticosteroids control inflammation and itching
• Antihistamines provide relief for symptoms
• Sun protection strategies, including sunscreen and protective clothing are crucial

Polymorphic Light Eruption

• A common type of idiopathic photodermatosis (skin reaction to sunlight with unknown cause).
• Characterized by a red, itchy, or burning rash that appears on sun-exposed areas like the face, neck, and arms.
• Rash develops hours to days after UV exposure, often during spring and summer.
• Lesions can appear as papules, plaques, or vesicles (small bumps, flat raised areas, or fluid-filled blisters).
• Symptoms usually resolve spontaneously within days, but lesions may recur with further sun exposure.
• The exact cause is unknown, but genetics and an exaggerated immune response to UV radiation are thought to play a role.
• Environmental factors, such as altitude, reflective surfaces (sand, water), and certain medications or photosensitizers, can exacerbate the condition.
• Treatment involves avoiding sun exposure, using broad-spectrum sunscreen, and using topical corticosteroids to reduce inflammation and itching.
• Oral antihistamines can provide relief from itching.
• UV phototherapy can be used as a preventative measure in recurrent cases.
• Immunosuppressive therapy is a last resort for severe and resistant cases.

This quiz covers various skin reactions induced by extreme temperatures, including cold-induced rashes, erythema ab igne, and miliaria. Learn about symptoms, treatments, and the effects of prolonged exposure to cold and heat on skin health.