Mary’s swollen face was not the result of ten rounds with a boxer – maybe soft fruit was to blame

“You’re allergic to something.” “I thought so,” she said. “But I haven’t changed my washing powder or anything.”

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Mary looked like she’d been on the wrong end of an encounter with Tyson Fury – her lips were huge and misshapen, and her eyes were so swollen she could barely see. I thought it was brave of her to have sat in the crowded waiting room. It’s a tight-knit community, and her appearance could easily have generated gossip. Her husband, Neville, also in his early 70s, had advanced dementia, and his behaviour can be physically challenging – could Mary have been on the receiving end of an aggressive outburst?

But the swelling distorting Mary’s features was not caused by trauma – there was a telltale rubberiness to it, and no associated bruising.

“And I’ve this terribly itchy rash,” she said. She pulled up a sleeve: florid red weals.

“You’re allergic to something.”

“I thought so,” she said. “But I haven’t changed my washing powder or anything.”

It never fails to warm my heart how often patients cite laundry detergent as the number one suspect for any skin eruption. While I’ve seen several cases over the years it’s nothing like as common as people suppose. The pattern of Mary’s reaction suggested a very different cause. The rash was typical for urticaria, otherwise known as hives; the facial swelling was the result of something termed angioedema, which occasionally appears in conjunction with urticaria.

I explained that urticaria and angioedema are provoked by ingested allergens, rather than by anything coming into contact with the skin. The swelling and itch are mediated by histamine, and high-dose anti-histamines will usually dampen things down over a few days. But if possible we needed to work out what had set it off so that Mary could avoid future exposure.

“Have you eaten anything out of the ordinary?” I asked. She didn’t think so. It’s surprisingly difficult to remember what we ate even a day before, though, so I prompted her with some common possibilities: “Shellfish, nuts, strawberries?” She shook her head, “Nothing like that, no.”

Medication is another frequent precipitant. I quizzed her about over-the-counter remedies – humble ibuprofen can spark angioedema – but she hadn’t taken anything. She was prescribed a couple of drugs for high blood pressure, but she’d been on them for years, so it seemed unlikely. I was stumped. I was still pondering whether to try withdrawing one of her medications, when Mary suddenly piped up.

“Actually, I did have strawberries last night.” I was briefly excited: this must be it. As swiftly as my hopes were raised, they were dashed. “But I’ve been eating them all summer.”

I was ready to admit defeat. It’s not always possible to identify the allergen behind urticaria/angioedema; it was going to be a question of keeping fingers crossed that Mary wouldn’t encounter it again. I started prescribing her some potent anti-histamines, but she had clearly continued to turn things over in her memory.

“Mind you, those strawberries last night, they were from Sainsbury’s.”

I stopped what I was doing.

“I usually shop at Asda,” she explained. “But those ones last night, they were from Sainsbury’s.”

I did a quick online literature search and found a paper from Germany describing the widely varying levels of an allergen – known as the Fra a 1 protein – present in different varieties of strawberry. Mary, caught up in the detective chase, promised to dig out the packaging from her bin. She handed them in to my bemused receptionist that afternoon. The Sainsbury’s punnet had contained a cultivated variety called Favori. Asda’s packaging didn’t specify, but its customer care helpline traced the variety from the product code: it was an entirely different kind.

Favori didn’t feature in the German scientists’ analysis. The only way of knowing whether it was responsible for Mary’s urticaria/angioedema would be for her to try eating them again. Understandably, she’s decided to stick with her usual Asda supplies, and thus far she’s remained allergy-free. 

Next week: Tracey Thorn

This article appears in the 11 September 2019 issue of the New Statesman, Cameron’s legacy of chaos