Mosquitoes belonged to the family of nematocerid flies which was the Culicidae (from the Latin culex, genitive culicis, meaning "midge" or "midge"). The female mosquito was responsible for carrying the vector that leads to the spread of the disease. There were 3000 species of mosquitoes, but there were mainly 3 mosquitoes responsible for the spread of diseases in humans. First, the voracious Asian tiger mosquito, a member of the Aedes family, carrier of yellow fever, dengue and encephalitis. Subsequently, the malarial disease was transmitted by Anopheles mosquitoes. They also transmit filariasis (also called elephantiasis) and encephalitis. Finally, Culex mosquitoes carry encephalitis, heartworm, and West Nile virus. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get Original EssayRecently, there have been many cases related to mosquito diseases that have spread globally. The Americas were hit by a massive Zika virus (ZIKV) epidemic that affected at least 49 states in early 2013-2014. Although most cases have occurred in South America and the Caribbean, imported and indigenous cases have occurred in the United States. The vectors of ZIKV were known as Aedes a Egypti and Aedes albopictus mosquitoes. Most populations are unaware of the possibility that Aedes mosquitoes in temperate zones transmit the ZIKV virus. Aedes vexans has worldwide dispersal, is very abundant in particular locations, aggressively stings humans, and is a competent vector of several arboviruses (Gendernalik, 2017). Zika was a viral disease spread by the bite of two infected mosquito species and was an emerging disease in the Western Hemisphere. People who have been bitten by a mosquito infected with the Zika virus often show only minor, if any, symptoms. Major Zika concerns, however, include the virus's documented impact on pregnancies and sexual transmission of the virus. The other common mosquito disease now spreading throughout the world was malaria. According to an article in The Herald, according to the Ministry of Health, the country (Zimbabwe) has recorded a significant increase in malaria cases compared to the same period in the last two years. Dr Mberkunashe said that in the first 11 weeks of this year, 119,593 cases were recorded compared to 73,019 and 82,328 cases in the same periods in 2016 and 2015 (Mawonde, 2017). In May 2015, the first reports of locally transmitted Zika infection received by the World Health Organization (WHO) from Brazil. Subsequently, in October 2015, WHO received reports that mothers exposed to the Zika virus during pregnancy cause microcephaly in infants. As of February 2016, local transmission of Zika infection has been reported from more than 20 countries, including the Americas, and a number of outbreaks in the thousands. of the cases occurred in Cape Verde, West Africa. (Kindhauser et al., 2016). In addition to this, based on the researchers of Kindhauser et al. (2016), serological tests (antibody detection) for Zika cross-react with antibodies stimulated by other viral infections, the presence of Zika virus was ideally confirmed by detection of viral nucleic acids by polymerase chain reaction (PCR) testing or by the isolation of the virus. Plectranthus amboinicus (Lour.) Spreng was a perennial herbaceous plant belonging to the Lamiaceae family, widespread in the tropics and warm areas of Africa, Asia and Australia (Arumugam et al., 2016). A large genus of Plectranthus of the Lamiaceae familyit includes 300 different species and can be found in tropical Africa, Asia and Australia (Lukhoba et al., 2006). This plant is also commonly known as Indian borage and was a fleshy, succulent herb famous for its distinctive oregano-like flavor and odor (Arumugam et al., 2016). IBO can be used as a food flavoring, food additive and natural non-toxic preservative (botanical fungicide) replacing chemical fungicides.2.2.2 AdvantagesPlectranthus Amboinicus was a plant widely practiced as a traditional medical specialty plant for the treatment of diseases such as cough, fever and others. It was used in folk medicine to treat conditions such as colds, asthma, constipation, headaches, coughs, fevers, and skin diseases (Arumugam et al., 2016). According to researcher Patel et.al (2010), “the results show that ethanolic and aqueous extracts of Plectranthus amboinicus had significant antioxidant activity”. In addition to this, (Manjamalai et al., 2012) found that Plectranthus Amboinicus essential oil showed substantial anti-inflammatory and antimicrobial action. In addition to its medicinal properties, it also possesses antifungal, antiochratoxigenic and antioxidant activities to protect food products from microbes (Murthy et.al, 2008). Additionally, Plectranthus species were often used as medicines and were used to treat a variety of ailments, skin infections, digestive system problems, and respiratory problems (Lukhoba et al., 2006). The aromatic leaves of Plectranthus amboinicus (Lour.) Spreng can be used to prepare a syrup and researchers have shown that it can be used to treat coughs and has also been used to treat livestock (Rice et.al, 2011). Plectranthus amboinicus was used to treat skin ulcerations caused by Leishmania braziliensis in Brazil, and the juice of this plant was used to treat skin allergies in India. It has also been used as a poultice for centipede and scorpion bites in Malay and also to treat burns (Lukhoba et.al, 2005). Gurgel et.al (2009) stated that “we have reported that P. amboinicus hydroalcoholic possesses promising anti-inflammatory and anti-tumor effects”. It may seem that Plectranthus amboinicus has many benefits in treating many diseases.2.2.3 Bioactive CompoundBioactive compound was a type of chemical found in small amounts in plants and some foods (such as fruits, vegetables, nuts, oils, and whole grains ). Bioactive compounds have actions in the body that can promote good health. Previous studies demonstrate prevention of cancer, heart disease and other diseases (National Cancer Institute). Examples of bioactive compounds present in Plectranthus Amboinicus were carvacrol, thymol, Cis –caryophyllene, t-caryophyllene and p-cymene. Furthermore, Arumugam et al. (2016) state that the main components of the aerial parts (stem and leaves) of P.amboinicus collected in Thailand were linalool (50.3%), carvacrol (14.3%), geranyl acetate (11.7%) and nerol acetate (11.6%) with transcription factor inhibitory activity. Furthermore, carvacrol constituent, along with other components such as p-cymene, b-caryophyllene, and a-terpinolene were the bioactive compounds that could be the reason for the antifungal activity (Murthy et al., 2009). In Cuba, a leaf was boiled and administered to patients suffering from chronic cough or tuberculosis, and finally, scientific studies have shown that P. amboinicus has anti-Mycobacterium tuberculosis activity. Furthermore, unsterilized ethanolic extract of P. amboinicus leaves showed antibacterial activity against diabetic wound pathogens, S. aureus, P. mirabilis, E. coli, K. pneumonia, and P. aeruginosa (Arumugam et al.,2016). So, it can be seen that the bioactive compound of this plant was very useful for medical purposes. 2.3 Essential Oil Extraction There were many extractions and now it was widely used to extract the bioactive compound from the herbal plant. The desired bioactive compound was very important for medicinal purposes. Many of them were established to perform various types of important functions in living plants such as attraction, protection or signaling. The definition of bioactive compound in plants concerns secondary plant metabolites that show pharmacological or toxicological effects in humans and animals (Azmir et al., 2013). The extraction types widely used to extract essential oil from herbaceous plants were such as hydrodistillation (Chen et. al, 2014), ultrasonic extraction (Wang and Lee, 2016), ultrasonic, microwave, Soxhlet extraction and cold maceration ( Wu et al, 2015).2.4 Lotion FormulationThe extraction of essential oils from the herbal plant can be used to produce lotion, cream by adding it with a certain amount of it. It has been important to promote the bioactive compounds of Plectranthus Amboinicus, such as thymol and carvacrol, as mosquito repellents for the skin. Many diseases have been proven due to mosquito bites such as Zika, dengue, encephalitis and yellow fever. Some mosquitoes were disease vectors. This implies that they can carry diseases from one human or animal to another. Typically, diseases were caused by tiny parasites or viruses. For example, a mosquito that bites an infected human or creature can pick up a virus along with its blood meal and spread it to other people through their bites. The higher amount of carvacrol and thymol as bioactive compound in Plectranthus Amboinicus essential oils may cause the cases of mosquito-borne diseases are reduced. The small amount of Plectranthus Amboinicus essential oil extract was used in the lotion formulation as an active ingredient to promote the lotion as an insect repellent. The basic components to form a lotion or cream were thickener, emulsifier, humectant, diluent, emollient and others. The aim of this work is to optimize the formulation of mosquito repellent lotion using Plectranthus Amboinicus leaf essential oil extract by varying the emulsifier, thickener and essential oil. Table 2.4.1 shows the various types of thickeners used in industry today. According to the table, the suitable thickener to use in the lotion formulation is a synthetic thickener such as carbopol. According to Table 2.4.5, the suitable emulsifier used in this formulation was an oil-in-water emulsifier such as glyceryl monostearate. The oil-in-water emulsifier was suitable for the lotion formulation because the consistency of the lotion was too non-oily mixture and the function of the emulsifier was supported by the oil drops packed in water, used for moisturizing effects. The selection of the emulsifier was based on the calculation of the HLB (hydrophilic-lipophilic balance). Lipid thickeners Lipid thickeners mainly consisted of liquid materials. They give the formula their natural thickness. Normally, these materials can be liquefied by heat and solid at room temperature. They were mainly used in creams and lotions. Some frequent types include carnauba wax, stearyl alcohol, cetyl alcohol, and stearic acid. Naturally Derived Thickeners The natural thickener component was made up of polymers that work by absorbing water to swell and gain viscosity. Cellulose derivatives such as hydroxyethyl cellulose were commonly used in liquid cleansing products such as body wash or shampoo. Guar gum was another example of.