Understanding Rash in 3 minutes. Skin Rash types and causes.

Types of Skin lesion
Skin rash means changing human skin appearance and or texture.
Different diseases cause different types of skin lesions. And the first critical step is to determine what kind of lesion is presented.
We will discuss the most common type of rash.

Papules.
Papules are Raised, solid lesions, well-defined bump in the skin, which a diameter of less than 5 mm.
Papules can be different colors, from flash colors to blue, red, black or yellow.
Papules can be presented in case of fungal infections, eczema, psoriasis, and secondary syphilis.
Macules.
Macules are flat, without elevation or depression, so nonpalpable, well or ill-defined lesions. Big macules are called patches.
Macules are: vitiligo, moles, freckles, sun spots, and age spots.
Plaques.
Plaques can be described as broad papules which are less then 5 mm. or flat, plateau-like lesions.
Plaque can be caused by:
Eczema, Psoriasis, Pityriasis Rosea, Ringworm and Tinea Versicolor.
Nodules.
Nodules are more than 5 mm in diameter, more rounded shape lesions. Nodules look like big papules.
Nodules may form on tendons and muscles in response to injury.
Also common on vocal cords. They occur in conditions including endometriosis, neurofibromatosis, and in rheumatoid arthritis
Wheals.
Wheals (urticaria, hives) - are papules or plaques, with red, raised, itchy bumps. they are pink-colored and transient. Most of them will disappear in 24 hours. Fewer than 5% of cases last for more than six weeks. Hives frequently occur following an infection or as a result of an allergic reaction.
Vesicles.
Vesicles 5 mm diameter circumscribed, elevated lesions filled with fluid. Common examples of vesicle formation are infections: Herpes simplex (cold sores, genital herpes) and chickenpox.
Bullae
Bullae look like vesicles but are bigger in diameter. More than 5 mm.
Friction is the One of the most common causes of bullae.
Pustules.
Pustules are vesicles that contain purulent exudate.
acne and folliculitis are classical examples of pustule formation.
Purpura.

 
Purpura is a flat lesion due to bleeding into the skin.
If purpura is smaller than 3 mm. it is called petechiae. And if it is larger than 3 mm, it is called ecchymosis.
Palpable purpura is due to inflammation of the vascular wall.
An ulcer is a skin lesion extended at least into the upper layer of the dermis.
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