Using a dedicated tool would be preferable to the blade method. When you use the blade, you could break the tick and leave some parts in the tissue (according to my sources thatīs still better than leaving it attached).
Many people use oil to suffocate the tick. That softens the skin and makes it easier to remove the tick. The disadvantage is that you increase the risk of an infection as you stated. Therefore this method is obsolete.
New first aid information doesnīt spread too fast so itīs no surprise that a lot of obsolete information is still in use.
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If it isnīt broken, it doesnīt have enough features yet.