Mang kapa mang a ka angoa ke letlalo le omeletseng ka nako e 'ngoe. Batho ba bang ba na le letlalo le omeletseng ka lebaka la liphatsa tsa bona tsa lefutso, ba bang ba ka utloa bohloko ka linako tse ling bophelong ba bona ka lebaka la mabaka a ka ntle. Ho hlokomela letlalo le omeletseng, ke habohlokoa ho tseba litšoaneleho tsa eona le ho khetholla metsoako e sebetsang e hlokahalang hore e lule e le ntle.

Letlalo ke setho se pharaletseng ka ho fetisisa 'meleng oa motho kaha le emela 16% ea boima ba eona kaofela. E phetha karolo e 'maloa ea bohlokoa' meleng: letlalo le re sireletsa khahlanong le liketso tse mabifi tsa ka ntle (litšisinyeho, tšilafalo ...), e thusa 'mele ho laola mocheso oa eona, e kenya letsoho tlhahisong ea vithamine D le lihomone le ho re sireletsa khahlanong le tsona. tšoaetso ka sesole sa eona sa 'mele (e etelletsoeng pele ke keratinocyte). Letlalo la rona le hlophisitsoe ka mekhahlelo e mengata.

Letlalo ke setho se rarahaneng se hlophisitsoeng ka mekhahlelo e 'maloa e kopanang:

• Sesosa sa epidermis: e mabapi le bokaholimo ba letlalo e entsoeng ka mefuta e meraro ea lisele: keratinocyte (motsoako oa keratin le lipids), melanocyte (lisele tse etsang hore letlalo le be le 'mala) le lisele tsa langherans (tsamaiso ea 'mele ea ho itšireletsa mafung ea letlalo). Epidermis e bapala karolo ea ts'ireletso hobane e na le semi-permeable. 
• The dermis, lera le bohareng : E fumaneha tlas'a epidermis 'me e e tšehetsa. E arotsoe ka mekhahlelo e 'meli, e leng papillary dermis le reticular dermis e nang le lipheletsong tsa methapo le likhoele tse rekere. Likarolo tsena tse peli li na le li-fibroblasts (tse hlahisang collagen) le lisele tsa 'mele tsa ho itšireletsa mafung (histiocyte le lisele tsa mast). 
• Hypoderme, karolo e tebileng ya letlalo : e laced tlas'a dermis, hypodermis ke lisele tsa adipose, ke hore li entsoe ka mafura. Methapo le methapo ea mali li feta ka har'a hypodermis ho ea dermis. Hypodermis ke sebaka sa polokelo ea mafura, e sireletsa masapo ka ho sebetsa e le ntho e senyang maikutlo, e boloka mocheso le ho bopa silhouette.

Likarolo tsena tse fapaneng li na le 70% ea metsi, 27,5% ea protheine, 2% ea mafura le 0,5% ea letsoai la liminerale le trace elements.

Letlalo le omileng ke mofuta oa letlalo, joalo ka letlalo le mafura kapa le kopaneng. E khetholloa ka ho tiea, ho thothomela le matšoao a bonahalang a letlalo a kang ho ba mahoashe, ho phunya le letlalo le lerootho. Batho ba nang le letlalo le omeletseng le bona ba ka ba le ho tsofala hoa letlalo ho feta tse ling (makhopho a tebileng). Lebaka le ka sehloohong la letlalo le omeletseng ke ho haella ha lipids: litšoelesa tsa sebaceous li hlōleha ho hlahisa sebum e lekaneng ho etsa filimi e sireletsang letlalong. Ho tiea le ho hlohlona ha letlalo ho boetse ho etsahala ha letlalo le felloa ke metsi, sena se bitsoa ho omella ka nako ha letlalo. Potsong, mabifi a ka ntle a kang a batang, moea o omileng, tšilafalo, letsatsi, empa hape le ho haella ha hydration ka hare le ka ntle. Botsofali le bona ke kotsi ea ho omella hobane ha nako e ntse e feta, metabolism ea letlalo e ea fokotseha.

Ka hona, letlalo le omeletseng le hloka ho feptjoa le ho tšeloa metsi ka botebo. hydration ea letlalo e qala ka phepelo e ntle ea metsi. Ke ka lebaka leo ho khothalletsoang ho noa lilithara tse 1,5 ho isa ho tse 2 tsa metsi ka letsatsi. Ho feta moo, batho ba nang le letlalo le omeletseng ba tlameha ho sebelisa lihlahisoa tsa tlhokomelo ea letsatsi le letsatsi tse nang le lisebelisoa tse ngata tse nkiloeng ka metsi, lintho tsa tlhaho tse mongobo (tseo hape li bitsoang Natural Moisturizing Factors kapa NMF) le lipids ho e fepa ka botebo. 

Molek'hule ea linaleli ka tlhokomelo ea letlalo ka lilemo tse 'maloa, urea ke e' ngoe ea Lintho tsa Tlhaho tsa Moisturizing, tse bitsoang "hygroscopic" agents. Li-NMF ka tlhaho li teng ka har'a corneocyte (lisele tse ka har'a epidermis) 'me li na le karolo ea ho hohela le ho boloka metsi. Ho phaella ho urea, ho na le lactic acid, amino acid, lik'habohaedreite le li-ion tsa diminerale (chloride, sodium le potasiamo) har'a li-NMF. 

Urea 'meleng e tsoa ho ho senyeha ha liprotheine ke' mele. Molek'hule ena e entsoe ke sebete 'me e tlosoa ka har'a moroto. Urea e fumanoang tlhokomelong ea letlalo e kolobisang e se e entsoe ka laboratoring ho tsoa ho ammonia le carbon dioxide. E mamelloa hantle ke mefuta eohle ea letlalo, urea e tumme ka keratolytic ea eona (e ntša letlalo ka bonolo), antibacterial le moisturizing (e monya le ho boloka metsi). Ka ho tlama limolek'hule tsa metsi, urea e li boloka likarolong tse ka holimo tsa epidermis. Ka hona, molek'hule ena e loketse ka ho khetheha bakeng sa letlalo le nang le li-calluses, letlalo le nang le li-acne, letlalo le bonolo le letlalo le omeletseng.