This document discusses various parasitic infections and insect bite hypersensitivity. It describes different types of parasitic infections caused by arthropods, insect bites, worms and protozoa. These include paederus dermatitis, myiasis, pediculosis, scabies, filariasis, larva migrans, pinworm infestation and cysticercosis. It then focuses on insect bite hypersensitivity, noting that the causative insect varies by region and can include mosquitoes, bugs and fleas. The skin reaction is due to pharmacologically active substances or microorganisms introduced during the bite. Clinical features include lesions appearing in recurrent crops most frequently in summer/rainy seasons. The prototype lesion is a pap

1. Parasitic Infections

2. • Arthropods
• Insect bites
• Paederus dermatitis
• Myiasis
• Pediculosis
• Scabies
• Parasitic Worms
• Filariasis
• Larva migrans
• Pinworm infestation
• Cysticercosis
• Protozoal Diseases
• Leishmaniasis

3. Insect Bite Hypersensitivity (IBH)
• ETIOLOGY
• Causative insect varies from region to region and includes
mosquitoes, bugs, fleas, etc.
• When an insect bites, the skin reaction could be due to:
• Pharmacologically active substances: chemicals like
histamine and proteases injected by arthropods cause
immediate reaction.
• Microorganisms: introduced into the skin during the bite
or due to scratching may result in:
• Pyoderma.
• Vector-borne diseases.

4. • Clinical Features
• Onset
• Lesions appear in recurrent crops, most frequently
• in summer and rainy season.
• Morphology
• Prototype lesion: Is called papular urticaria
• which has two components:
• Immediate reaction:
• Is due to direct action of pharmacologically
• active substances injected.
• A wheal (Fig. 16.1A) which appears within
• a few minutes of insect bite.
• Lasts few minutes—couple of hours. May
• evolve into a papule.
Variants:
• Bullous papular urticaria:
• Seen in children.
• Frank vesicles and bullae, which frequently
• get secondarily infected.
• Most frequently occur on legs.