Marine algae are rich in a variety of biologically and pharmacologically active substances. They are considered as a resource that has been used by humans to some extent . Nowadays, algal biomass is a renewable source of many valuable bioactive substances, having a wide array of applications in many industries, such as food, chemical, agricultural, pharmaceutical, cosmetic, medical. The present work focuses on the impact of algae on the human body. The potential use of algae and algal extracts in medicine and cosmetic industry is discussed. Due to the antibacterial, antiviral, antifungal, anti-inflammatory properties, algae can be used in the curing of many types of diseases [7, 8]. These properties result from the biologically active compounds present in the biomass of algae. The components of the algae that may help in the treatment tumor diseases are: polyphenols , polysaccharides , carrageenan [33–35], fucoidan [24, 30–32], fucoxanthin , diterpenes [27–29] or monoterpenes . Substances extracted from algae with anti-inflammatory, antipyretic and analgesic include: fucosterol , porphyrins , lactones, phenols, carbohydrates , polysaccharides [51, 53, 54], fucoidan , galactan , fucan . Fucoxanthin [64–68], fucoidan , triacyloglycerols , polyphenols  or phlorotannin  can be used as anti-obesity agents. Overreaction of the immune system to harmless environmental substances can be minimized by the use of antiallergic substances, which include mainly phlorotannins [73, 77, 78] and fatty acids [79, 80]. The components of algae, such as polysaccharides [99–101], diterpenes , bromophenol , carbohydrates , fucans [96, 97], galactans , carrageenan , fucoidan  or galactofucan  could be successfully utilized against various types of viruses. It has been proved that algae show dermatological and cosmetic properties: anti-inflammatory and bactericidal action (due to the presence of zinc) [8, 9, 19, 113], increase of the flexibility of the skin (peptides and vitamins) [13, 104, 105], improve blood circulation of the skin and thanks to the alginic acid they treat erythema [13, 103]. They influence on of inhibition of sebum secretion and on other problems of oily skin. Algae are used in many cosmetics to tone up the skin, lighten stretch marks [104, 111, 112]. Compresses made of algae slenderize and eliminate cellulite. A field of skin cosmetics called Thalassotherapy is a form of therapy that uses marine climate, sea water, mud, algae, sand and other substances derived from the sea as a therapeutic agents [13, 103].