Born on a farm in West Cork, Cairns is a farmer working in the family business, Brown Envelope Seeds, producing organic seeds. She has a first class honours MSc in Organic Horticulture from University College Cork. Her mother, Madeline McKeever, contested the 2004 Skibbereen Town Council election as a Green Party candidate. Madeline McKeever, noted as an environmental activist in West Cork: The People and the Place, was arrested in 2003 alongside Quentin Gargan for selling home produce on the street in Skibbereen. A subsequent court case found that their market stalls were legal, to the benefit of other would-be market traders.
Cairns was elected to Cork County Council for the Bantry–West Cork local electoral area in the 2019 local elections, winning the last seat by a single vote, after several rechecks and a recount. Cairns ran on a platform opposing the establishment of a plastics factory in Skibbereen. RTP, the company proposing the factory later withdrew their planning application. After the application was withdrawn, Cairns said that "It also highlights the fact that councillors need to look carefully at rezoning and local area plans to make sure they are in line with government policy on climate change. We can’t keep flying the green flag and shy away from taking real climate action decisions. She received publicity as a result of four of her posters disappearing in the Durrus area after the first official day of postering. Cairns was offered a year as Mayor by Fine Gael in return for support, which she turned down. She stood for Chair of the Municipal District of West Cork, but was beaten by Cllr. Joe Carroll by 5 votes to 4. She produces the "Inside the Chamber" podcast about local government. Cairns campaigns for greater transparency in local government. In late 2019, she raised a motion to ensure that representatives should receive documents three days before having to vote on them. The motion was passed by 53 out of 54 councillors.She revealed how the head of the local authority, Tim Lucey, told her that staff were upset by what she suggested in her motion. During an episode of "Inside the Chamber", she said that he told her staff felt the nature of the motion on her Facebook page ‘was derogatory.’ Defending herself, she said she had just explained her experience ‘honestly and truthfully.’ Describing the Council staff as ‘amazing’, she said: ‘I wasn’t insinuating that anyone was doing a shabby job. I was just saying how it is and I’ll continue to do that. I was very surprised to be told that it was derogatory to do my job.’ She said that getting hefty documents and reports before a meeting started impeded her from doing her job properly and said "When my motion was passed, the chief executive referred it to the Corporate Policy Group to iron out the details. But I found out last week that behind closed doors, the Corporate Policy Group decided that receiving the documents at 9am before an 11am meeting was absolutely fine. This is outrageous. I can’t believe it happened. I will not stand for it. I refuse to be a rubber stamp for Cork County Council." She was publicly supported by Social Democrats co-leader, Catherine Murphy TD. Following her election to the Dail in 2020, Ross O'Connell, a 29 year old Goleen based PhD student and environmental scientist, was co-opted onto Cork County Council in her place.
TD (2020-present)
2020 General Election
Cairns contested the 2020 general election as a candidate in the Cork South West constituency. She was listed by The Irish Mirror as the youngest Social Democrats candidate, being 30 years old. Cairns was described by the Irish Times during the election campaign as being from Turkhead, west of Skibbereen. She received recognition from The Guardian, as she was running against her boyfriend, Christopher O'Sullivan, stating 'I feel a bit like I'm in a badly written rom-com'. She was elected, taking the third and final seat, receiving 4,696 first preference votes, the fifth highest amount overall. Heading into the eighth count, Cairns was 2,078 votes behind Fine Gael Senator Tim Lombard, but Cllr Paul Hayes of Sinn Féin saw 3,023 of his transfers go to her and 393 to Lombard, before being deemed elected with 10,078 votes. Cairns was the only female TD elected in all of Cork City and county. Cairns is the Social Democrat Spokesperson for agriculture. In March 2020, the ICMSA hit out at Cairns' 'airy-fairy criticism' of dairy export sectors. Eileen Calnan, Chairperson of the West Cork ICMSA, said that she was ‘somewhat taken aback’ by what she called Deputy Cairn’s ‘lukewarm and half-hearted’ support of the local dairy sector in a recent interview on RTE Radio 1’s Countrywide. Cairns replied that as farmers, herself and Ms Calnan had more in common than they had to differ on. ‘I’m glad that we can agree on the most important thing of all: that farmers must be paid a fair price for their product. What I don’t agree with is the notion that it’s “airy-fairy” to acknowledge that there are many aspects of the way we do things right now that are not sustainable. It’s unreasonable to think the sector isn’t vulnerable and doesn’t need more robust support in the face of climate change..before this election, Ms Calnan said farmers didn’t want politicians who just told them what they thought they wanted to hear. I am delighted to be able to say that that is a promise I will always be able to keep.’ Also in March, speaking on the fishing industry, Cairns called on Minister Michael Creed to set up a task force involving all stakeholders, from those fishing to the processors and retailers.
Twitter Controversy
In late February 2020, Cairns apologised for comments unearthed by the Irish news websiteGript in tweets from 2012 and 2013. This included comments that said; “The pope is gonna get so cyber bullied, can’t wait. #pope #vatican" in December 2012 and “For every minute of air time taken up on the papal conclave I’m gonna get an abortion #pope”, on the day of the election of Pope Francis on 13 March 2013. Three days later Cairns wrote: "New paedophile-ring-leader Describes Gay Adoption as 'Child Abuse'," with a link to an article. Cairns is described as having sent a number of other tweets that were highlighted referencing aspects of the Catholic Church over 2012 and 2013, linking to articles, including one from TheJournal.ie which referenced the Pope’s former butler taking the stand in a leaks trial. “The pope feels abused...How awful!” she tweeted alongside a link to the article. Cairns, who was 22 when she sent the tweets, has issued an apology for her comments. “I apologise for the offence caused. The comments were made a long time ago, when I was a lot younger and the wording was inappropriate. The comments were made 8 years ago in the context of the Ireland we lived in then, where things like equal marriage and repeal were a long way off. I phrased things badly and apologise that my choice of words caused offence for some people.”” she told The Echo. She told Independent.ie that; "I was much younger and they weren't the best-advised tweets" and "I regret any offence caused. I took them down for that reason. I am really sorry for any offence caused."A spokeswoman for the Social Democrats said: "It was seven years ago, Holly was much younger and clearly they weren't the best-advised tweets. She sincerely regrets any offence she may have caused."
Personal life
Her partner, Christopher O'Sullivan, is a Fianna Fáil TD. Both successfully contested the same constituency in 2020.
