The lines as you are describing mostly suggest the urticatrial reaction. It is the type of the allergy/
hypersensitivity that you have feced because of contact with or the ingestion of some known or unknown allergen.
As you are saying you neither have chancged laundry nor the soaps the chances food born allergy are likely.
Most common foods whcih might be responsible for such reactions are bringels, sea food such as prawns or crabs , gavar etc. though any food substance can give rise to such reaction.
You should be careful and attentive while having these foods.
Now you can have following medications
Tab Levocetrizine 5 mg two times a day
Cap
omeprazole two times a day before food . bothe medications for five days .
If irritation or itching is there you can apply any soothening agent.
Caution avoid driving after having tab levocetrizine as it may cause
drowsiness in few patients
In case of swelling extends to face , difficulty in breathing, difficulty in swallowing rush immidiatly to the ER as it may suggest the signs of angioneurotic oedema which may be fatal.