difference between eczema, rash and blotch and their meanings

[Learning_English]

Could anyone tell me, what is the difference between (eczema, rash, blotch)
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Please let me know if I have made any mistakes in any of my sentences.

[Mister Micawber]

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From various online medical dictionaries:

rash: Lay term for a cutaneous eruption.

eczema: Generic term for inflammatory conditions of the skin, particularly with vesiculation in the acute stage, typically erythematous, edematous, papular, and crusting; followed often by lichenification and scaling and occasionally by duskiness of the erythema and, infrequently, hyperpigmentation; often accompanied by sensations of itching and burning; the vesicles form by intraepidermal spongiosis; often hereditary and associated with allergic rhinitis and asthma.

blotch: a blemish or spot.
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Native English teacher at Mister Micawber's