What’s special about Tristan da Cunha? Well, it calls itself “the world’s remotest island" – at least, in the South Atlantic. But it’s also distinguished by having a population of 266 people, nearly half of whom have asthma. Allergy Planet (BBC2) was a serious Horizon documentary (for once) studying the mysterious increase in the number of people suffering from allergies. It started by saying of allergy that “50 years ago it barely existed” but it was more than 50 years ago when, as a child, I was diagnosed as being allergic to eggs (which give me asthma). People can be allergic to all sorts of things, including nuts, dogs, cats, dust, milk, shellfish and chocolate. Allergens can induce distressing reactions and even cause death.

What causes so many modern allergies? It might be urbanisation or pollution from motor vehicles, although Tristan da Cunha has never experienced traffic pollution and it is hardly urbanised. Tristan is peopled by the descendants of only seven families, which suggests that the asthma may be of genetic origin. Or are allergies caused by our passion for cleanliness, which damages our skin (a natural barrier against allergy)? Or is it the proliferation in our homes of carpets, upholstery and bedding – ideal hideouts for dust-mites? The programme concluded: “An effective mass treatment for allergies is still a long way off.”

I may be developing an allergy to Top Gear (BBC2). I quite like Jeremy Clarkson’s penchant for attacking sacred cows like global warming and speed cameras, but his jokes on the programme are increasingly sinking to the depths plumbed by Jonathan Ross and Russell Brand. Clarkson seems to have learnt nothing from the outcry caused by his recent insulting remarks about lorry drivers.

In this week’s programme, Jeremy and his macho pals investigated if any Communist country had ever produced a good car. As a test site they used Greenham Common airbase, which Jeremy described as “home in the 1980s to 96 US Air Force nuclear missiles and several hundred lesbians”.

As if this remark wasn’t offensive enough, Jeremy called the Morris Marina “Trotskyite crap” and his sidekick (James “get your hair cut” May) dragged in an outdated reference to Arthur Scargill’s communist leanings. Top Gear used to be a programme about motor cars but it has turned into a self-congratulatory celebration of old-fashioned chauvinism.

Russian Communism certainly had an effect on St Petersburg’s Mariinsky Theatre, which was the subject of Sunday’s South Bank Show (ITV1). Lenin wanted to shut it down, as it represented alien culture, but later leaders like Khrushchev used it as a showplace to impress foreign dignitaries. In 1935 it was unnecessarily renamed the Kirov after the assassinated leader of the Leningrad Communist party.

The theatre premiered operas and ballets by the likes of Glinka, Tchaikovsky, Mussorgsky and Prokofiev. It fostered the careers of such stars as Chaliapin, Nijinsky, Pavlova, Mravinsky, Baryshnikov and Nureyev – although Communism drove some of them to seek asylum in the West. But the theatre was important to the country because, as one ballerina said, “without culture, Russia is so poor”.

Thankfully, the Mariinsky has been revived under the directorship of Valery Gergiev and recently added a new concert hall to its facilities. The documentary was interesting but bitty: trying to trace the theatre’s history without a commentary. It may have mystified viewers who have never visited the Mariinsky or St Petersburg.

Television is full of makeover shows: mostly transforming human bodies but also renovating or saving houses. The latest is Country House Rescue (Channel 4), in which Ruth Watson tries to help the owners of country houses to revive their fortunes.

In the first programme, the owner of a medieval manor house in Somerset was resistant to Ruth’s modernising ideas, and at one point she said “We’re not THAT stupid, Ruth.” Yet, like many factual TV programmes, this one kept reminding us of what we had already been told. We are not THAT stupid.