People who have hayfever can save 75 per cent off their tablet bills at the till, it has been warned. A code on pills could mean you could slash the amount you're forking out at Tesco, Morrisons, Boots and Superdrug as spring arrives.

Own-label tablets sold in most major supermarkets and chemists have identical formulas, which you can work out by looking at the product licence (PL) number. One drug containing 10mg of Loratadine - PL number 16028/0080 - is available for 6p each in Aldi, in packs of 14 for 79p.

But it is also on sale for 20p each in Boots, in 30-packs for £5.99, a study has found. Dr José Costa, a senior paediatric allergy consultant for thechildrensallergy.co.uk service, said of the two drugs: "If the PL codes are the same, the dose and ingredients are identical, therefore the effect on allergy relief will also be exactly the same.

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“So it's worth looking at the codes to check you're paying the best price." Oli Townsend, assistant deals editor at MoneySavingExpert, added: “This happens across many medications where prices totally differ for the exact same tablets, so it’s important to be vigilant and check the PL number to ensure you’re not just paying extra for prettier packaging.

"Even if PL numbers don’t match, you can slash the cost of tablets by looking where the active ingredient is the same – that’s the key ingredient that matters – the rest are largely irrelevant, unless you have allergies. You can opt for a cheaper unbranded or own-brand tablet over one of the more expensive big brands with the same active ingredient that'll do the same thing."

A Boots spokesperson said: “At Boots we offer a wide range of hay fever medicines, including own brand products, at a range of price points. Our pharmacy team members are available in stores to help customers find the right solutions for them.

“We regularly run promotions on hayfever products and our Advantage Card members can unlock 10% off Boots own brand.”