Fear about the mosquito-borne Zika virus has sparked a surge in Brazilians rushing to buy repellant, creating a shortage of some brands on shop shelves.
Following the detection of Zika in April, sales of repellant in Brazil rose by one-third last year, according to consumer research firm Nielsen.
That has doubled revenue for the sector to US$55.7 million.
Buying was also spurred by an increase in cases of dengue, another virus spread by the Aedes aegypti mosquito.
Sales have risen even more sharply since Brazilian authorities in November flagged a potential link between Zika and suspected cases of microcephaly, a condition marked by abnormally small head size in newborns that can result in developmental problems.
Even at small local pharmacies in Rio, waiting lists for the most sought-after repellant, Exposis, stretch to hundreds of names, with expectant mothers and their families rushing from store to store in search of the product.
Raia Drogasil, Brazil's largest chain of pharmacies, said repellant sales in December jumped seven-fold from a year earlier.
Brazil's biggest retailer, the Pao de Acucar Group , said supermarket sales of repellant were up 120 percent in the first weeks of 2016, compared to the same period a year earlier.
The rise was sharpest in the Northeast region at the centre of the outbreak, where sales rose fourfold, and in the Brazil's second city of Rio de Janeiro, where they tripled.
In Rio, protection against Zika is a top priority for the city's 6.5 million inhabitants and hundreds of thousands of tourists as the country's biggest Carnival celebration kicks off on Friday (local time) and the Olympic Games start in August.
Exposis, developed by France's Osler, has received media attention in Brazil because it is the only brand on the market with the active ingredient Icaridin. Many Brazilians consider it the most effective repellant against the Aedes mosquito, though studies suggest its efficacy is similar to brands using DEET.
Cristiane Padrao, a 36-year-old physical education teacher in her sixth month of pregnancy, said she could not find Exposis anywhere despite scouring the internet and enlisting the help of family in other parts of Brazil.
"I'm on my third tube of it," she said. "I bought one in Rio. My sister was able to buy one in Belo Horizonte and my mother bought two for me" in Minas Gerais state north of Rio.